ICSE – Grade 10 – Physics – Ch 06 – QA

Questions & Answers

ICSE - Grade - 10

Subject: Physics

Chapter - 06 - Spectrum

Types of Questions

MCQ

  1. What causes deviation of light in a triangular prism?
    A. Reflection
    B. Refraction
     C. Diffraction
     D. Scattering
     Answer: B. Refraction

 

  1. The angle between the incident ray and emergent ray is called:
    A. Angle of incidence
    B. Angle of refraction
     C. Angle of deviation
     D. Prism angle
     Answer: C. Angle of deviation

 

  1. Which colour of white light deviates the most in a prism?
    A. Red
    B. Blue
     C. Green
     D. Violet
     Answer: D. Violet

 

  1. Which colour has the highest frequency in white light?
    A. Red
    B. Indigo
     C. Violet
     D. Green
     Answer: C. Violet

 

  1. What is the wavelength range of red light?
    A. 400–450 nm
    B. 590–620 nm
     C. 620–750 nm
     D. 495–570 nm
     Answer: C. 620–750 nm

 

  1. Dispersion of white light is due to:
    A. Same angle of deviation for all colours
    B. Different wavelengths of colours
     C. Scattering of light
     D. Absorption in prism
     Answer: B. Different wavelengths of colours

 

  1. Which wave has the longest wavelength in the electromagnetic spectrum?
    A. Gamma rays
    B. X-rays
     C. Radio waves
     D. Ultraviolet rays
     Answer: C. Radio waves

 

  1. Which of the following electromagnetic radiations is used for cancer treatment?
    A. X-rays
    B. Infrared rays
     C. Gamma rays
     D. Ultraviolet rays
     Answer: C. Gamma rays

 

  1. What is the discoverer of X-rays?
    A. Becquerel
    B. Newton
     C. Roentgen
     D. Curie
     Answer: C. Roentgen

 

  1. Which radiation causes skin cancer in high doses?
    A. Infrared
    B. Ultraviolet
     C. Microwave
     D. Radio
     Answer: B. Ultraviolet

 

  1. What is the frequency range of green light?
    A. 530–510 THz
    B. 610–530 THz
     C. 630–610 THz
     D. 790–670 THz
     Answer: B. 610–530 THz

 

  1. What is the wavelength range of infrared radiation?
    A. 400–800 nm
    B. Below 0.01 nm
     C. 800–10⁶ nm
     D. 1–400 nm
     Answer: C. 800–10⁶ nm

 

  1. Which radiation causes fluorescence on a zinc sulphide screen?
    A. Infrared
    B. Ultraviolet
     C. Microwave
     D. Radio
     Answer: B. Ultraviolet

 

  1. What causes the blue colour of the sky?
    A. Refraction
    B. Reflection
     C. Scattering
     D. Interference
     Answer: C. Scattering

 

  1. Which effect is used to study particle size in colloids?
    A. Doppler Effect
    B. Tyndall Effect
     C. Compton Effect
     D. Hall Effect
     Answer: B. Tyndall Effect

 

  1. Which electromagnetic wave is used in microwave ovens?
    A. Infrared
    B. Microwaves
     C. UV
     D. Radio waves
     Answer: B. Microwaves

 

  1. Which light wave has the shortest wavelength?
    A. Red
    B. Blue
     C. Violet
     D. Green
     Answer: C. Violet

 

  1. Which of these rays has the highest energy?
    A. X-rays
    B. Infrared
     C. Gamma rays
     D. Ultraviolet
     Answer: C. Gamma rays

 

  1. In the electromagnetic spectrum, visible light lies between:
    A. UV and X-rays
    B. Infrared and UV
     C. Radio and Infrared
     D. Microwave and Radio
     Answer: B. Infrared and UV

 

  1. What is the cause of the red colour at sunrise and sunset?
    A. Dispersion
    B. Reflection
     C. Maximum scattering of red light
     D. Minimum scattering of red light
     Answer: D. Minimum scattering of red light

 

  1. Which wave is used in satellite communication?
    A. Gamma rays
    B. Microwaves
     C. UV rays
     D. X-rays
     Answer: B. Microwaves

 

  1. Which radiation is most effective in heating?
    A. Gamma rays
    B. UV rays
     C. X-rays
     D. Infrared rays
     Answer: D. Infrared rays

 

  1. Which wave does not affect photographic plates?
    A. Ultraviolet
    B. Infrared
     C. X-rays
     D. Visible light
     Answer: B. Infrared

 

  1. Which wave is detected by the human eye?
    A. X-rays
    B. Gamma rays
     C. Infrared
     D. Visible light
     Answer: D. Visible light

 

  1. What is the speed of all EM waves in vacuum?
    A. 3×10⁶ m/s
    B. 3×10⁸ m/s
     C. 3×10¹⁰ m/s
     D. 3×10⁵ m/s
     Answer: B. 3×10⁸ m/s

 

  1. Which part of the spectrum is used in medical X-rays?
    A. Gamma rays
    B. UV rays
     C. X-rays
     D. Infrared rays
     Answer: C. X-rays

 

  1. What happens to white light in a prism?
    A. Reflects
    B. Splits into components
     C. Absorbs
     D. Deflects without change
     Answer: B. Splits into components

 

  1. Which wave is below 0.01 nm in wavelength?
    A. Gamma rays
    B. X-rays
     C. UV rays
     D. Visible light
     Answer: A. Gamma rays

 

  1. Who discovered visible light?
    A. Newton
    B. Roentgen
     C. Marconi
     D. Hertz
     Answer: A. Newton

 

  1. What is the cause of light scattering?
    A. Refraction at glass
    B. Reflection from metal
     C. Particles in the medium
     D. Magnetic fields
     Answer: C. Particles in the medium

 

  1. Which radiation causes heating of a thermometer’s blackened bulb?
    A. UV
    B. X-rays
     C. Infrared
     D. Visible
     Answer: C. Infrared

 

  1. Which wave is produced in crystal oscillators?
    A. Radio
    B. Microwave
     C. X-ray
     D. UV
     Answer: B. Microwave

 

  1. Which radiation cannot pass through glass but can pass through quartz?
    A. Ultraviolet
    B. Visible
     C. Infrared
     D. Microwave
     Answer: A. Ultraviolet

 

  1. Which colour has the longest wavelength?
    A. Violet
    B. Blue
     C. Orange
     D. Red
     Answer: D. Red

 

  1. What is the unit of wavelength commonly used in optics?
    A. Ampere
    B. Angstrom
     C. Newton
     D. Watt
     Answer: B. Angstrom

 

  1. Which EM radiation is used in sterilization?
    A. Microwave
    B. UV
     C. X-ray
     D. Infrared
     Answer: B. UV

 

  1. What is the phenomenon where light spreads in various directions due to particles?
    A. Reflection
    B. Diffraction
     C. Scattering
     D. Absorption
     Answer: C. Scattering

 

  1. Which radiation is used in remote controls?
    A. UV
    B. Infrared
     C. Radio
     D. Visible
     Answer: B. Infrared

 

  1. What effect is observed in a beam of light through a smoke-filled room?
    A. Raman Effect
    B. Tyndall Effect
     C. Compton Effect
     D. Hall Effect
     Answer: B. Tyndall Effect

 

  1. X-rays are absorbed by:
    A. Soft tissues
    B. Glass
     C. Bones
     D. Quartz
     Answer: C. Bones

 

  1. Which radiation causes chemical changes in dyes?
    A. UV
    B. Microwave
     C. Gamma
     D. Radio
     Answer: A. UV

 

  1. Which EM wave was discovered by Hertz?
    A. X-rays
    B. Radio waves
     C. Microwaves
     D. Infrared
     Answer: C. Microwaves

 

  1. What is the function of aerials in radio receivers?
    A. Transmit energy
    B. Receive sound
     C. Detect microwaves
     D. Detect radio waves
     Answer: D. Detect radio waves

 

  1. What is the main property of gamma rays?
    A. Fluorescence
    B. Strong heating
     C. High penetration
     D. Long wavelength
     Answer: C. High penetration

 

  1. Which colour has wavelength approx. 5000 Å to 5780 Å?
    A. Blue
    B. Green
     C. Yellow
     D. Indigo
     Answer: B. Green

 

  1. In dispersion, which factor causes separation of colours?
    A. Reflection
    B. Wavelength
     C. Speed
     D. Brightness
     Answer: B. Wavelength

 

  1. Which wave cannot be seen but has strong heating effect?
    A. UV
    B. X-rays
     C. Gamma
     D. Infrared
     Answer: D. Infrared

 

  1. Which wave affects both photographic plates and human skin?
    A. UV
    B. Microwave
     C. Infrared
     D. Visible
     Answer: A. UV

 

  1. Which part of EM spectrum is used in thermal imaging?
    A. Gamma
    B. Microwave
     C. Infrared
     D. UV
     Answer: C. Infrared

 

  1. Blue light is scattered more than red due to:
    A. Greater speed
    B. Shorter wavelength
     C. Higher mass
     D. Higher energy
     Answer: B. Shorter wavelength

Fill in the Blanks

  1. The phenomenon of splitting white light into its constituent colours is called __________.
    Answer: dispersion

 

  1. The colour of white light that bends the most in a prism is __________.
    Answer: violet

 

  1. The angle between the incident ray and the emergent ray in a prism is called __________.
    Answer: angle of deviation

 

  1. White light is made up of __________ colours.
    Answer: seven

 

  1. The wavelength range of red light is __________.
    Answer: 620–750 nm

 

  1. The electromagnetic wave with the shortest wavelength is __________.
    Answer: gamma rays

 

  1. The wave that is used in satellite communication is __________.
    Answer: microwaves

 

  1. The phenomenon responsible for the blue colour of the sky is __________.
    Answer: scattering

 

  1. The phenomenon of light scattering in colloids is known as the __________ effect.
    Answer: Tyndall

 

  1. All electromagnetic waves travel at the speed of __________ in vacuum.
    Answer: 3×10⁸ m/s

 

  1. The wave used for medical imaging of bones is __________.
    Answer: X-rays

 

  1. The wave that causes skin tanning and sunburn is __________.
    Answer: ultraviolet

 

  1. The range of visible light is from __________ to __________ nanometres.
    Answer: 400 to 800

 

  1. The electromagnetic wave used in TV and radio transmission is __________.
    Answer: radio waves

 

  1. The radiation that is most strongly felt as heat is __________.
    Answer: infrared

 

  1. Violet light has the __________ wavelength in visible light.
    Answer: shortest

 

  1. Red light has the __________ frequency in visible light.
    Answer: lowest

 

  1. The scattering of light depends on the __________ of the particles.
    Answer: size

 

  1. __________ is the scientist who discovered X-rays.
    Answer: Roentgen

 

  1. The process by which light changes direction at the interface between two media is __________.
    Answer: refraction

 

  1. The electromagnetic wave that can pass through rock salt but not through glass is __________.
    Answer: infrared

 

  1. The electromagnetic wave that can pass through quartz but not through glass is __________.
    Answer: ultraviolet

 

  1. The visible spectrum is also called the __________ spectrum.
    Answer: continuous

 

  1. Gamma rays are used in the treatment of __________.
    Answer: cancer

 

  1. The colour with wavelength approximately 5000 Å to 5780 Å is __________.
    Answer: green

 

  1. In a prism, light bends due to __________ at its surfaces.
    Answer: refraction

 

  1. The electromagnetic radiation discovered by Herschel is __________.
    Answer: infrared

 

  1. The unit commonly used to express wavelength in optics is __________.
    Answer: angstrom

 

  1. Microwaves are produced by __________ oscillators.
    Answer: crystal

 

  1. The EM wave that causes fluorescence in zinc sulphide is __________.
    Answer: ultraviolet

 

  1. Infrared radiation was discovered by __________.
    Answer: Herschel

 

  1. The blue colour of the sky is due to the scattering of __________ wavelengths.
    Answer: shorter

 

  1. The red colour of sunrise and sunset is due to the scattering of __________ wavelengths.
    Answer: shorter

 

  1. The continuous band of colours formed due to dispersion is called the __________.
    Answer: spectrum

 

  1. The electromagnetic radiation used for sterilization of surgical instruments is __________.
    Answer: ultraviolet

 

  1. The electromagnetic wave with the longest wavelength is __________.
    Answer: radio waves

 

  1. The photographic film gets affected most by __________ rays.
    Answer: X-rays

 

  1. The part of white light that has the highest frequency is __________.
    Answer: violet

 

  1. The radiation that causes maximum heating effect is __________.
    Answer: infrared

 

  1. The colour with the least deviation in a prism is __________.
    Answer: red

 

  1. X-rays are absorbed by __________ in the human body.
    Answer: bones

 

  1. The energy of an electromagnetic wave is directly proportional to its __________.
    Answer: frequency

 

  1. The splitting of white light occurs because each colour has a different __________.
    Answer: wavelength

 

  1. The scattering of light in a smoke-filled room is an example of the __________ effect.
    Answer: Tyndall

 

  1. The electromagnetic wave that affects dyes and photographic plates is __________.
    Answer: ultraviolet

 

  1. A thermometer with a blackened bulb rises quickly when exposed to __________ radiation.
    Answer: infrared

 

  1. The EM wave discovered by Marconi is __________.
    Answer: radio waves

 

  1. The electromagnetic wave that lies just beyond the red end of visible light is __________.
    Answer: infrared

 

  1. The electromagnetic wave that lies just beyond the violet end of visible light is __________.
    Answer: ultraviolet

 

  1. The range of gamma rays is typically below __________ nanometres.
    Answer: 0.01

Name the Following

  1. Name the phenomenon of splitting white light into different colours.
    Answer: Dispersion

 

  1. Name the device used to produce a spectrum from white light.
    Answer: Triangular prism

 

  1. Name the seven colours of the visible spectrum.
    Answer: Violet, Indigo, Blue, Green, Yellow, Orange, Red

 

  1. Name the colour with the shortest wavelength.
    Answer: Violet

 

  1. Name the colour with the longest wavelength.
    Answer: Red

 

  1. Name the wave used in medical imaging of bones.
    Answer: X-rays

 

  1. Name the wave that is strongly felt as heat.
    Answer: Infrared

 

  1. Name the radiation responsible for sunburns.
    Answer: Ultraviolet

 

  1. Name the wave with the longest wavelength in the electromagnetic spectrum.
    Answer: Radio waves

 

  1. Name the wave with the shortest wavelength in the electromagnetic spectrum.
    Answer: Gamma rays

 

  1. Name the scientist who discovered infrared radiation.
    Answer: Herschel

 

  1. Name the scientist who discovered ultraviolet radiation.
    Answer: Ritter

 

  1. Name the scientist who discovered X-rays.
    Answer: Roentgen

 

  1. Name the scientist who discovered radio waves.
    Answer: Marconi

 

  1. Name the phenomenon responsible for the blue colour of the sky.
    Answer: Scattering of light

 

  1. Name the phenomenon that makes the sun appear red during sunset.
    Answer: Scattering of light

 

  1. Name the effect responsible for the visibility of a beam of light in dusty air.
    Answer: Tyndall effect

 

  1. Name the unit used to measure wavelength in optics.
    Answer: Angstrom

 

  1. Name the type of spectrum formed by dispersion of white light.
    Answer: Continuous spectrum

 

  1. Name the colour in white light that deviates the most.
    Answer: Violet

 

  1. Name the colour in white light that deviates the least.
    Answer: Red

 

  1. Name the wave used for sterilising surgical instruments.
    Answer: Ultraviolet

 

  1. Name the wave used in satellite communication.
    Answer: Microwaves

 

  1. Name the electromagnetic wave used in remote controls.
    Answer: Infrared

 

  1. Name the electromagnetic wave used in television transmission.
    Answer: Radio waves

 

  1. Name the property of EM waves that remains constant in vacuum.
    Answer: Speed

 

  1. Name the angle formed between the incident and emergent ray in a prism.
    Answer: Angle of deviation

 

  1. Name the device used to detect X-rays.
    Answer: Photographic plate

 

  1. Name the visible light spectrum band discovered by Newton.
    Answer: Visible spectrum

 

  1. Name the radiation that can pass through quartz but not through glass.
    Answer: Ultraviolet

 

  1. Name the radiation that can pass through rock salt but not through glass.
    Answer: Infrared

 

  1. Name the electromagnetic wave that produces fluorescence.
    Answer: Ultraviolet

 

  1. Name the wave used in microwave ovens.
    Answer: Microwaves

 

  1. Name the electromagnetic wave with frequency just below that of visible light.
    Answer: Infrared

 

  1. Name the electromagnetic wave with frequency just above that of visible light.
    Answer: Ultraviolet

 

  1. Name the rays emitted by radioactive substances.
    Answer: Gamma rays

 

  1. Name the radiation used for treating cancer.
    Answer: Gamma rays

 

  1. Name the effect seen when light passes through a colloidal solution.
    Answer: Tyndall effect

 

  1. Name the colour in white light with a wavelength range of 495–570 nm.
    Answer: Green

 

  1. Name the colour in white light with a frequency range of 480–400 THz.
    Answer: Red

 

  1. Name the electromagnetic radiation that causes chemical changes in dyes.
    Answer: Ultraviolet

 

  1. Name the electromagnetic radiation that produces the maximum heating effect.
    Answer: Infrared

 

  1. Name the electromagnetic radiation detected by the human eye.
    Answer: Visible light

 

  1. Name the wave used for thermal imaging.
    Answer: Infrared

 

  1. Name the wave that can cause skin cancer on prolonged exposure.
    Answer: Ultraviolet

 

  1. Name the electromagnetic radiation that affects photographic plates the most.
    Answer: X-rays

 

  1. Name the wave with wavelength range below 0.01 nm.
    Answer: Gamma rays

 

  1. Name the part of EM spectrum used in FM radio.
    Answer: Radio waves

 

  1. Name the range of wavelength for visible light.
    Answer: 400–800 nm

 

  1. Name the speed at which all electromagnetic waves travel in vacuum.
    Answer: 3 × 10⁸ m/s

Answer in One Word

  1. What is the phenomenon of splitting light into colours called?
    Answer: Dispersion

 

  1. Which colour deviates the most in a prism?
    Answer: Violet

 

  1. Which colour has the longest wavelength?
    Answer: Red

 

  1. Which radiation is used in X-ray imaging?
    Answer: X-rays

 

  1. Which radiation has the highest frequency?
    Answer: Gamma

 

  1. Which wave is used in remote controls?
    Answer: Infrared

 

  1. Which radiation is responsible for skin tanning?
    Answer: Ultraviolet

 

  1. What is the speed of light in vacuum (in scientific notation)?
    Answer: 3×10⁸

 

  1. Which radiation causes the maximum heating effect?
    Answer: Infrared

 

  1. What unit is commonly used to measure wavelength in optics?
    Answer: Angstrom

 

  1. Which scientist discovered infrared radiation?
    Answer: Herschel

 

  1. Which scientist discovered ultraviolet radiation?
    Answer: Ritter

 

  1. What phenomenon causes the sky to appear blue?
    Answer: Scattering

 

  1. What is the colour of sunlight during sunrise?
    Answer: Red

 

  1. What phenomenon makes light deviate in a prism?
    Answer: Refraction

 

  1. Which radiation is used in sterilization?
    Answer: Ultraviolet

 

  1. Which part of the spectrum is visible to the human eye?
    Answer: Visible

 

  1. Which EM wave is used in satellite communication?
    Answer: Microwave

 

  1. Which radiation has the shortest wavelength?
    Answer: Gamma

 

  1. Which wave is used in thermal imaging?
    Answer: Infrared

 

  1. What is the angle between incident and emergent rays called?
    Answer: Deviation

 

  1. Which radiation lies just beyond red in the spectrum?
    Answer: Infrared

 

  1. Which radiation lies just beyond violet in the spectrum?
    Answer: Ultraviolet

 

  1. Which spectrum consists of seven visible colours?
    Answer: Continuous

 

  1. What is the common name for VIBGYOR?
    Answer: Spectrum

 

  1. What is the range of visible light in nanometres?
    Answer: 400–800

 

  1. Which colour has the highest frequency?
    Answer: Violet

 

  1. Which colour has the lowest frequency?
    Answer: Red

 

  1. Which radiation is used for cancer treatment?
    Answer: Gamma

 

  1. Which radiation affects photographic plates and dyes?
    Answer: Ultraviolet

 

  1. What effect explains light scattering in colloids?
    Answer: Tyndall

 

  1. Which electromagnetic wave is used in FM radio?
    Answer: Radio

 

  1. What is the basic cause of dispersion in a prism?
    Answer: Wavelength

 

  1. What is the frequency range unit for visible light?
    Answer: Terahertz

 

  1. What radiation is absorbed by bones in imaging?
    Answer: X-rays

 

  1. What is the unit of frequency in the electromagnetic spectrum?
    Answer: Hertz

 

  1. What do we call a beam of separated colours?
    Answer: Spectrum

 

  1. Which light is scattered least in the atmosphere?
    Answer: Red

 

  1. Which EM wave is used in mobile communication?
    Answer: Microwave

 

  1. Which radiation produces fluorescence?
    Answer: Ultraviolet

 

  1. Which scientist discovered X-rays?
    Answer: Roentgen

 

  1. What is the property common to all EM waves in vacuum?
    Answer: Speed

 

  1. What is the phenomenon that makes the sun appear red at sunset?
    Answer: Scattering

 

  1. What wave is produced by crystal oscillators?
    Answer: Microwave

 

  1. Which colour has a wavelength of around 5000 Å?
    Answer: Green

 

  1. Which electromagnetic wave is used in radar systems?
    Answer: Microwave

 

  1. What is the main source of visible light?
    Answer: Sun

 

  1. Which wave is most penetrating?
    Answer: Gamma

 

  1. Which radiation does not pass through glass but passes through quartz?
    Answer: Ultraviolet

 

  1. What wave is responsible for vision?
    Answer: Visible

ICSE - Grade 10 - Physics

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ICSE - Grade 10 - Mathematics

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  • Ch 1 – Earth as a Planet
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Find the Odd Man Out

  1. Violet, Indigo, Green, X-rays
    Answer: X-rays
    Explanation: X-rays are not part of visible light; others are.

 

  1. Infrared, Radio, Microwave, Blue
    Answer: Blue
    Explanation: Blue is visible light; the others are invisible EM waves.

 

  1. Gamma rays, X-rays, Red, UV
    Answer: Red
    Explanation: Red is part of visible spectrum; others are beyond visible range.

 

  1. Newton, Roentgen, Ritter, Herschel
    Answer: Newton
    Explanation: Newton studied visible light; others discovered non-visible EM waves.

 

  1. Radio waves, Microwaves, Infrared, Violet
    Answer: Violet
    Explanation: Violet is visible; the others are outside visible range.

 

  1. Scattering, Reflection, Refraction, Cancer
    Answer: Cancer
    Explanation: Cancer is a health effect; others are optical phenomena.

 

  1. Infrared, X-rays, Violet, UV
    Answer: Violet
    Explanation: Violet is visible light; others are not.

 

  1. Gamma rays, UV rays, Infrared, Microwave
    Answer: UV rays
    Explanation: UV is high-frequency; others are low-frequency EM waves.

 

  1. Tyndall Effect, Dispersion, Scattering, Evaporation
    Answer: Evaporation
    Explanation: Evaporation is a thermal process, not an optical phenomenon.

 

  1. Angstrom, Terahertz, Hertz, Celsius
    Answer: Celsius
    Explanation: Celsius measures temperature; others are wave-related units.

 

  1. Refraction, Diffraction, Radiation, Reflection
    Answer: Radiation
    Explanation: Radiation is energy transfer; others involve bending of light.

 

  1. Red, Yellow, Green, X-rays
    Answer: X-rays
    Explanation: X-rays are not part of the visible spectrum.

 

  1. Radio, Microwave, Infrared, Indigo
    Answer: Indigo
    Explanation: Indigo is visible; others are outside visible spectrum.

 

  1. Prism, Lens, Mirror, Antenna
    Answer: Antenna
    Explanation: Antenna is for waves; others are optical instruments.

 

  1. Roentgen, Curie, Herschel, Ritter
    Answer: Curie
    Explanation: Curie worked with radioactivity, not EM wave discovery.

 

  1. Red, Violet, Spectrum, Angstrom
    Answer: Angstrom
    Explanation: Angstrom is a unit; others are light-related terms.

 

  1. Sterilization, Vision, Photography, Cancer therapy
    Answer: Cancer therapy
    Explanation: Cancer therapy uses gamma rays, not visible light.

 

  1. Glass, Quartz, Rock-salt, Water
    Answer: Water
    Explanation: Water is not a typical optical medium used in EM transmission.

 

  1. Microwave, Radar, TV transmission, Infrared camera
    Answer: Infrared camera
    Explanation: Infrared camera detects heat, not used for communication.

 

  1. Ultraviolet, Blue, Green, Red
    Answer: Ultraviolet
    Explanation: UV is invisible; others are visible light colours.

 

  1. Radio waves, Microwaves, IR waves, UV waves
    Answer: UV waves
    Explanation: UV has higher frequency; others are low-frequency waves.

 

  1. Quartz, Rock-salt, Mirror, Glass
    Answer: Mirror
    Explanation: Mirror reflects; others transmit light.

 

  1. Reflection, Dispersion, Refraction, Penetration
    Answer: Penetration
    Explanation: Penetration relates to X-rays, not optical behaviour.

 

  1. Red, Yellow, Green, Infrared
    Answer: Infrared
    Explanation: Infrared is not visible; others are visible colours.

 

  1. Gamma, Alpha, Beta, X-rays
    Answer: Alpha
    Explanation: Alpha is a particle; others are EM radiations.

 

  1. Radio, X-ray, UV, Sound
    Answer: Sound
    Explanation: Sound is mechanical; others are electromagnetic.

 

  1. Green, Blue, Orange, Hertz
    Answer: Hertz
    Explanation: Hertz is a unit; others are colours.

 

  1. Microwave, Infrared, Ultraviolet, Green
    Answer: Green
    Explanation: Green is visible; others are not.

 

  1. Newton, Roentgen, Maxwell, Marconi
    Answer: Newton
    Explanation: Newton studied optics; others contributed to EM wave science.

 

  1. Wavelength, Frequency, Mass, Energy
    Answer: Mass
    Explanation: Mass is not a wave property.

 

  1. UV, Visible, IR, Sound
    Answer: Sound
    Explanation: Sound is not an EM wave.

 

  1. Air, Vacuum, Water, Antenna
    Answer: Antenna
    Explanation: Antenna is not a medium.

 

  1. Sunlight, Electric bulb, Fluorescent lamp, Oven
    Answer: Oven
    Explanation: Oven emits infrared, not visible light.

 

  1. Gamma, X-ray, UV, Red
    Answer: Red
    Explanation: Red is visible; others are high-energy invisible radiations.

 

  1. Frequency, Energy, Time, Wavelength
    Answer: Time
    Explanation: Time is not a direct wave parameter.

 

  1. Blue, Yellow, UV, Indigo
    Answer: UV
    Explanation: UV is invisible; others are visible.

 

  1. Photographic plate, Zinc sulphide, Thermometer, Convex lens
    Answer: Convex lens
    Explanation: Lens does not detect radiation; others do.

 

  1. Tyndall Effect, Scattering, Reflection, Sublimation
    Answer: Sublimation
    Explanation: Sublimation is a phase change, not optical.

 

  1. Green, Blue, Spectrum, Cancer
    Answer: Cancer
    Explanation: Cancer is a health effect, not light-related.

 

  1. Television, Oven, X-ray machine, Microscope
    Answer: Microscope
    Explanation: Microscope is optical, others use EM radiation.

 

  1. Terahertz, Angstrom, Joule, Hertz
    Answer: Joule
    Explanation: Joule is energy unit; others relate to wave properties.

 

  1. Glass, Quartz, Spectrum, Water
    Answer: Spectrum
    Explanation: Spectrum is not a material medium.

 

  1. Blue, Green, Yellow, Infrared
    Answer: Infrared
    Explanation: Infrared is invisible; others are visible.

 

  1. Radio, Microwave, UV, Red
    Answer: Red
    Explanation: Red is visible; others are not.

 

  1. Newton, Roentgen, Herschel, Fleming
    Answer: Fleming
    Explanation: Fleming is not associated with wave discovery.

 

  1. Radio, UV, X-ray, Convex mirror
    Answer: Convex mirror
    Explanation: It’s a device, not a wave.

 

  1. UV, IR, Gamma, Blue
    Answer: Blue
    Explanation: Blue is visible; others are not.

 

  1. Marconi, Maxwell, Roentgen, Faraday
    Answer: Roentgen
    Explanation: Roentgen discovered X-rays; others worked on EM waves.

 

  1. Infrared, Microwave, X-ray, Yellow
    Answer: Yellow
    Explanation: Yellow is visible; others are not.

 

  1. Green, Red, Blue, Cancer therapy
    Answer: Cancer therapy
    Explanation: It’s a medical application, not a light colour.

Match the Pair

Set 1 – Match the Pairs

Column A

  1. Dispersion
  2. Violet
  3. Refraction
  4. Infrared
  5. Roentgen

Column B
 A. Discovered X-rays
 B. Bending of light
 C. Splitting of white light
 D. Colour that deviates most
 E. Used in thermal imaging

Correct Answers:
 1 → C
 2 → D
 3 → B
 4 → E
 5 → A




Set 2 – Match the Pairs

Column A

  1. Scattering
  2. Ultraviolet
  3. Gamma rays
  4. X-rays
  5. Microwave

Column B
 A. Cancer treatment
 B. Sunburn
 C. Satellite communication
 D. Blue colour of the sky
 E. Bone imaging

Correct Answers:
 1 → D
 2 → B
 3 → A
 4 → E
 5 → C




Set 3 – Match the Pairs

Column A

  1. Red light
  2. Visible spectrum
  3. Tyndall effect
  4. Angstrom
  5. Newton

Column B
 A. Observed in colloids
 B. Unit of wavelength
 C. Least deviation
 D. Studied white light
 E. Continuous band of colours

Correct Answers:
 1 → C
 2 → E
 3 → A
 4 → B
 5 → D




Set 4 – Match the Pairs

Column A

  1. Gamma rays
  2. UV radiation
  3. Infrared radiation
  4. Radio waves
  5. Prism

Column B
 A. Produces spectrum
 B. Longest wavelength
 C. Fluorescence
 D. Sterilization
 E. Highest frequency

Correct Answers:
 1 → E
 2 → D
 3 → C
 4 → B
 5 → A




Set 5 – Match the Pairs

Column A

  1. Blue light
  2. Green light
  3. Red light
  4. Violet light
  5. Yellow light

Column B
 A. 495–570 nm
 B. 620–750 nm
 C. 380–450 nm
 D. 570–590 nm
 E. 450–475 nm

Correct Answers:
 1 → E
 2 → A
 3 → B
 4 → C
 5 → D




Set 6 – Match the Pairs

Column A

  1. Ritter
  2. Herschel
  3. Marconi
  4. Scattering
  5. Refraction

Column B
 A. Causes deviation
 B. Discovered ultraviolet rays
 C. Discovered radio waves
 D. Discovered infrared rays
 E. Responsible for red sunset

Correct Answers:
 1 → B
 2 → D
 3 → C
 4 → E
 5 → A




Set 7 – Match the Pairs

Column A

  1. UV rays
  2. IR rays
  3. X-rays
  4. Microwave
  5. Spectrum

Column B
 A. Remote control
 B. Fluorescent lamps
 C. Formed by dispersion
 D. Medical diagnosis
 E. Felt as heat

Correct Answers:
 1 → B
 2 → E
 3 → D
 4 → A
 5 → C




Set 8 – Match the Pairs

Column A

  1. Wavelength
  2. Frequency
  3. Energy
  4. Speed of light
  5. Hertz

Column B
 A. Unit of frequency
 B. Measured in joules
 C. Distance between wave crests
 D. Oscillations per second
 E. 3 × 10⁸ m/s

Correct Answers:
 1 → C
 2 → D
 3 → B
 4 → E
 5 → A




Set 9 – Match the Pairs

Column A

  1. Quartz
  2. Glass
  3. Rock salt
  4. UV rays
  5. IR rays

Column B
 A. Passes UV, blocks IR
 B. Blocks UV, passes visible
 C. Passes IR, blocks UV
 D. Passes through quartz
 E. Passes through rock salt

Correct Answers:
 1 → D
 2 → B
 3 → E
 4 → A
 5 → C



Set 10 – Match the Pairs

Column A

  1. Cancer
  2. Fluorescence
  3. Photographic plate
  4. Heating
  5. Remote sensing

Column B
 A. Affected by X-rays
 B. UV radiation
 C. Gamma rays
 D. Infrared radiation
 E. Satellite-based detection

Correct Answers:
 1 → C
 2 → B
 3 → A
 4 → D
 5 → E

Short Answer Questions  

  1. What is dispersion?
    Answer: Dispersion is the splitting of white light into its component colours when it passes through a prism.

 

  1. Which colour deviates the most in a prism?
    Answer: Violet deviates the most in a prism.

 

  1. What is the angle between the incident and emergent ray in a prism called?
    Answer: It is called the angle of deviation.

 

  1. Name the colours of the visible spectrum.
    Answer: Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

 

  1. Which wave has the shortest wavelength in the electromagnetic spectrum?
    Answer: Gamma rays have the shortest wavelength.

 

  1. What is the speed of electromagnetic waves in vacuum?
    Answer: 3 × 10⁸ m/s.

 

  1. Who discovered infrared radiation?
    Answer: Sir William Herschel.

 

  1. What is the wavelength range of visible light?
    Answer: Approximately 400 nm to 800 nm.

 

  1. What is the main cause of dispersion?
    Answer: Different colours of light have different refractive indices in the prism.

 

  1. Which radiation is strongly felt as heat?
    Answer: Infrared radiation.

 

  1. What causes the blue colour of the sky?
    Answer: Scattering of short-wavelength blue light by atmospheric particles.

 

  1. Which wave is used in satellite communication?
    Answer: Microwaves.

 

  1. Which electromagnetic wave is used for sterilisation?
    Answer: Ultraviolet rays.

 

  1. What type of spectrum is produced by white light?
    Answer: A continuous spectrum.

 

  1. Which radiation is used in cancer treatment?
    Answer: Gamma rays.

 

  1. Which scientist discovered ultraviolet radiation?
    Answer: Johann Ritter.

 

  1. Name a device that produces dispersion of light.
    Answer: Triangular prism.

 

  1. Which electromagnetic wave is used in night vision cameras?
    Answer: Infrared radiation.

 

  1. What is the unit used to measure frequency?
    Answer: Hertz (Hz).

 

  1. Which wave is used in remote controls?
    Answer: Infrared radiation.

 

  1. Why does the sun appear red at sunrise and sunset?
    Answer: Due to scattering of shorter wavelengths, leaving red light.

 

  1. What is the range of red light in nanometres?
    Answer: 620 nm to 750 nm.

 

  1. What is Tyndall Effect?
    Answer: It is the scattering of light by particles in a colloid.

 

  1. Which electromagnetic wave has the lowest frequency?
    Answer: Radio waves.

 

  1. What is the function of a prism in dispersion?
    Answer: It refracts different colours at different angles to separate them.

 

  1. What is the wavelength range of violet light?
    Answer: Approximately 380 nm to 450 nm.

 

  1. Name the part of EM spectrum used in FM radio.
    Answer: Radio waves.

 

  1. Which electromagnetic wave causes fluorescence?
    Answer: Ultraviolet radiation.

 

  1. Which radiation lies just beyond the red end of visible spectrum?
    Answer: Infrared radiation.

 

  1. Which radiation lies just beyond the violet end of visible spectrum?
    Answer: Ultraviolet radiation.

 

  1. What is the order of EM waves by increasing frequency?
    Answer: Radio → Microwave → Infrared → Visible → Ultraviolet → X-rays → Gamma rays.

 

  1. Which light has the highest frequency in visible spectrum?
    Answer: Violet light.

 

  1. What is the effect of UV radiation on skin?
    Answer: It can cause sunburn or skin cancer.

 

  1. Name one application of infrared radiation.
    Answer: Thermal imaging.

 

  1. What causes scattering of light?
    Answer: Interaction of light with small particles or molecules.

 

  1. What is meant by electromagnetic spectrum?
    Answer: It is the range of all types of electromagnetic radiation arranged by wavelength or frequency.

 

  1. Which wave is used in microwave ovens?
    Answer: Microwaves.

 

  1. What is the common property of all electromagnetic waves?
    Answer: They all travel at the same speed in vacuum.

 

  1. Why is ultraviolet radiation used for sterilisation?
    Answer: Because it kills bacteria and viruses.

 

  1. Which radiation is most energetic in the EM spectrum?
    Answer: Gamma rays.

 

  1. Which light has the least deviation in a prism?
    Answer: Red light.

 

  1. What unit is commonly used in optics to measure wavelength?
    Answer: Angstrom (Å).

 

  1. What is the effect of X-rays on photographic plates?
    Answer: They blacken photographic plates.

 

  1. What kind of radiation does a red-hot object emit?
    Answer: Infrared radiation.

 

  1. Name the radiation used to detect forged currency.
    Answer: Ultraviolet radiation.

 

  1. Which radiation passes through quartz but not through glass?
    Answer: Ultraviolet radiation.

 

  1. Which radiation passes through rock salt but not through glass?
    Answer: Infrared radiation.

 

  1. What kind of radiation is detected by human eyes?
    Answer: Visible light.

 

  1. Why is red light used in danger signals?
    Answer: Because it scatters the least and is visible from a long distance.

 

  1. What is the frequency range of visible light?
    Answer: Approximately 4 × 10¹⁴ Hz to 7.5 × 10¹⁴ Hz.

Puzzles

  1. I am the colour that deviates the least in a prism. Who am I?
    Answer: Red

 

  1. I am invisible but help you feel warmth. I begin with ‘I’. Who am I?
    Answer: Infrared

 

  1. I bend white light into seven colours. What am I?
    Answer: Prism

 

  1. I kill germs and start with ‘U’. What am I?
    Answer: Ultraviolet

 

  1. I have the highest frequency in the EM spectrum. What am I?
    Answer: Gamma rays

 

  1. Which comes next in this sequence: Radio, Microwave, Infrared, ?
    Answer: Visible

 

  1. I make the sky blue but vanish at night. What process am I?
    Answer: Scattering

 

  1. I was discovered by Roentgen and see through bones. What am I?
    Answer: X-rays

 

  1. When light passes through a prism, I am the process that splits it. What am I?
    Answer: Dispersion

 

  1. I am invisible, cause sunburns, and help sterilize. What am I?
    Answer: Ultraviolet rays

 

  1. I appear red during sunrise and sunset due to…?
    Answer: Scattering of shorter wavelengths

 

  1. I travel fastest in vacuum and need no medium. What am I?
    Answer: Electromagnetic wave

 

  1. Which colour of VIBGYOR is refracted the most?
    Answer: Violet

 

  1. What EM wave helps detect heat in night vision cameras?
    Answer: Infrared

 

  1. I produce a continuous spectrum from white light. What am I?
    Answer: Prism

 

  1. I help in heating food quickly and start with ‘M’. What am I?
    Answer: Microwave

 

  1. I reflect, refract, and scatter — but don’t need a medium. What am I?
    Answer: Light

 

  1. What spectrum can human eyes detect?
    Answer: Visible light

 

  1. I am used in weather satellites and radar. What EM wave am I?
    Answer: Microwave

 

  1. Why does the sky appear blue?
    Answer: Due to scattering of blue light

 

  1. I am the only EM wave that is visible. What am I?
    Answer: Visible light

 

  1. I am emitted by hot objects but not seen by the eye. What am I?
    Answer: Infrared

 

  1. Which wave is used to sterilize surgical tools?
    Answer: Ultraviolet

 

  1. I travel far, diffract well, and am used in radios. What am I?
    Answer: Radio wave

 

  1. I bend most when white light enters glass. What colour am I?
    Answer: Violet

 

  1. Which light is scattered least in the atmosphere?
    Answer: Red

 

  1. I can pass through your skin and help doctors see inside. What am I?
    Answer: X-rays

 

  1. I help forensic scientists detect bloodstains. What am I?
    Answer: Ultraviolet light

 

  1. What EM wave comes after ultraviolet in the spectrum?
    Answer: X-rays

 

  1. Why is the sun red at sunset?
    Answer: Longer atmospheric path scatters shorter wavelengths

 

  1. Which type of light is used in TV remotes?
    Answer: Infrared

 

  1. I appear when light slows down and bends. What am I?
    Answer: Refraction

 

  1. I am used in hospitals to kill cancer cells. What am I?
    Answer: Gamma rays

 

  1. Why do black clothes feel warmer in sunlight?
    Answer: They absorb more infrared radiation

 

  1. I am not visible, pass through fog, and carry heat. What am I?
    Answer: Infrared radiation

 

  1. What property is common to all EM waves in a vacuum?
    Answer: Speed (3 × 10⁸ m/s)

 

  1. I cause the white light to spread into colours. What am I?
    Answer: Dispersion

 

  1. I’m found just before gamma rays in the EM spectrum. What am I?
    Answer: X-rays

 

  1. I help detect forged currency using fluorescence. What am I?
    Answer: Ultraviolet light

 

  1. Why does glass not allow UV rays to pass through?
    Answer: It absorbs ultraviolet radiation

 

  1. I have the longest wavelength and the least energy. What am I?
    Answer: Radio waves

 

  1. Which EM wave follows visible light in the spectrum?
    Answer: Ultraviolet

 

  1. What wave is used in airport body scanners?
    Answer: X-rays

 

  1. Why are gamma rays dangerous to humans?
    Answer: They are ionizing and penetrate deep into tissues

 

  1. Why is red used in traffic signals?
    Answer: It has the longest wavelength and is visible from afar

 

  1. Which wave causes your skin to tan in sunlight?
    Answer: Ultraviolet rays

 

  1. I make sunlight feel warm. What am I?
    Answer: Infrared radiation

 

  1. Which wave is used in mobile phone communication?
    Answer: Microwave

 

  1. I’m not visible, not harmful, but cook your food. What am I?
    Answer: Microwave

 

  1. Which spectrum does not have any gaps or missing bands?
    Answer: Continuous spectrum

Difference Between:

  1. Difference between: Dispersion and Scattering
    Answer:
  • Dispersion is the splitting of white light into its constituent colours due to different refractive indices.
  • Scattering is the redirection of light in various directions by particles in the medium, depending on wavelength.

 

  1. Difference between: Refraction and Dispersion
    Answer:
  • Refraction is the bending of light when it passes from one medium to another.
  • Dispersion occurs when light separates into different colours due to varying refractive indices.

 

  1. Difference between: Spectrum and Spectrometer
    Answer:
  • Spectrum is the band of colours obtained after dispersion.
  • Spectrometer is an instrument used to study the properties of the spectrum.

 

  1. Difference between: Infrared rays and Ultraviolet rays
    Answer:
  • Infrared rays have longer wavelengths than visible light and are felt as heat.
  • Ultraviolet rays have shorter wavelengths than visible light and are not visible but can cause chemical reactions.

 

  1. Difference between: Visible spectrum and Electromagnetic spectrum
    Answer:
  • Visible spectrum includes only wavelengths visible to the human eye (approx. 400–750 nm).
  • Electromagnetic spectrum includes all types of EM waves from radio to gamma rays.

 

  1. Difference between: Radio waves and Gamma rays
    Answer:
  • Radio waves have the longest wavelengths and lowest frequencies.
  • Gamma rays have the shortest wavelengths and highest frequencies.

 

  1. Difference between: Red light and Violet light
    Answer:
  • Red light has the longest wavelength and deviates the least in a prism.
  • Violet light has the shortest wavelength and deviates the most.

 

  1. Difference between: Continuous spectrum and Line spectrum
    Answer:
  • Continuous spectrum contains all wavelengths without gaps (e.g., sunlight).
  • Line spectrum contains specific wavelengths emitted or absorbed by elements.

 

  1. Difference between: Microwaves and Infrared waves
    Answer:
  • Microwaves are used in communication and cooking; have slightly longer wavelengths.
  • Infrared waves are used in thermal imaging and are closer to visible light.

 

  1. Difference between: Monochromatic light and White light
    Answer:
  • Monochromatic light consists of a single wavelength (e.g., laser).
  • White light contains a mixture of all visible wavelengths.

 

  1. Difference between: Reflection and Refraction
    Answer:
  • Reflection is the bouncing back of light from a surface.
  • Refraction is the bending of light when it enters a different medium.

 

  1. Difference between: Speed of light in vacuum and Speed in glass
    Answer:
  • In vacuum, speed of light is maximum (3 × 10⁸ m/s).
  • In glass, speed is reduced due to higher refractive index.

 

  1. Difference between: Scattering in the atmosphere and Dispersion by prism
    Answer:
  • Scattering causes blue sky and red sunsets due to interaction with air particles.
  • Dispersion produces VIBGYOR due to different bending of colours in glass.

 

  1. Difference between: X-rays and Ultraviolet rays
    Answer:
  • X-rays have shorter wavelengths and penetrate deeper into tissues.
  • Ultraviolet rays have longer wavelengths and are absorbed at the surface.

 

  1. Difference between: Thermal imaging and Night vision goggles
    Answer:
  • Thermal imaging detects infrared radiation emitted by objects.
  • Night vision goggles amplify visible and near-infrared light.

 

  1. Difference between: Spectroscope and Spectrometer
    Answer:
  • Spectroscope is a simple device for visual spectrum analysis.
  • Spectrometer is a precise scientific instrument for measuring wavelength and deviation.

 

  1. Difference between: Transparent medium and Opaque medium
    Answer:
  • Transparent medium allows light to pass through with minimal scattering (e.g., glass).
  • Opaque medium does not allow light to pass (e.g., wood).

 

  1. Difference between: Primary colours and Secondary colours
    Answer:
  • Primary colours (red, green, blue) cannot be formed by mixing.
  • Secondary colours are formed by mixing two primary colours.

 

  1. Difference between: Natural spectrum and Artificial spectrum
    Answer:
  • Natural spectrum is produced by natural sources like the sun.
  • Artificial spectrum is produced using artificial sources like electric bulbs.

 

  1. Difference between: Wavelength and Frequency
    Answer:
  • Wavelength is the distance between two wave crests.
  • Frequency is the number of waves passing a point per second.

Assertion and Reason

  1. Both Assertion and Reason are true, and Reason is the correct explanation.
    B. Both Assertion and Reason are true, but Reason is not the correct explanation.
     C. Assertion is true, but Reason is false.
     D. Assertion is false, but Reason is true.

  2. Assertion: Violet light bends more than red light in a prism.
    Reason: Violet light has a longer wavelength than red light.
     Answer: C
     Explanation: Violet bends more, but it has a shorter wavelength, not longer.

 


  1. Assertion: Gamma rays are used for cancer treatment.
    Reason: Gamma rays have high energy and strong penetrating power.
     Answer: A
     Explanation: Both are true and reason explains the assertion.

 


  1. Assertion: Infrared radiation causes heating.
    Reason: Infrared radiation has low energy.
     Answer: B
     Explanation: Both are true, but heating is due to absorption, not low energy.

 


  1. Assertion: Scattering of light is responsible for blue colour of the sky.
    Reason: Blue light has the shortest wavelength among visible colours.
     Answer: A
     Explanation: Both are true and correctly linked.

 


  1. Assertion: Red light is scattered more than violet light.
    Reason: Red light has shorter wavelength than violet.
     Answer: D
     Explanation: Both statements are false.

 


  1. Assertion: X-rays affect photographic films.
    Reason: X-rays have high penetration and ionizing properties.
     Answer: A
     Explanation: Both true and correctly connected.

 


  1. Assertion: Dispersion occurs when white light passes through a prism.
    Reason: Different colours of light travel at different speeds in the prism.
     Answer: A
     Explanation: Both are true and reason correctly explains dispersion.

 


  1. Assertion: Ultraviolet radiation is used in sterilization.
    Reason: UV rays are visible and have low energy.
     Answer: C
     Explanation: UV is invisible and high-energy.

 


  1. Assertion: Infrared rays are used in thermal imaging.
    Reason: They are strongly absorbed by skin and produce heat.
     Answer: A
     Explanation: Both true and reason is correct.

 


  1. Assertion: Gamma rays lie beyond the ultraviolet in the spectrum.
    Reason: Gamma rays have the longest wavelength.
     Answer: C
     Explanation: Gamma rays are beyond UV, but they have the shortest wavelength.

 


  1. Assertion: Red light bends least in a prism.
    Reason: Red light has the highest frequency.
     Answer: C
     Explanation: Red bends least, but has lowest frequency.

 


  1. Assertion: The spectrum produced by dispersion is a continuous spectrum.
    Reason: The colours in the spectrum do not overlap.
     Answer: C
     Explanation: Spectrum is continuous, but colours do overlap slightly.

 


  1. Assertion: Microwave ovens use microwaves to heat food.
    Reason: Microwaves cause ionization of food molecules.
     Answer: C
     Explanation: Microwaves cause vibration of water molecules, not ionization.

 


  1. Assertion: UV rays can cause skin cancer.
    Reason: UV rays are ionizing radiations.
     Answer: A
     Explanation: Both are true and related.

 


  1. Assertion: Red light has the longest wavelength in visible light.
    Reason: Red light has the lowest frequency in visible spectrum.
     Answer: A
     Explanation: Both are true and explain each other.

 


  1. Assertion: Scattering of light increases with increase in wavelength.
    Reason: Red light scatters more than blue.
     Answer: D
     Explanation: Both statements are false.

 


  1. Assertion: X-rays are used in medical diagnosis.
    Reason: They are absorbed by soft tissues but pass through bones.
     Answer: C
     Explanation: X-rays pass through soft tissues but are absorbed by bones.

 


  1. Assertion: All EM waves travel at the same speed in vacuum.
    Reason: EM waves require a material medium to travel.
     Answer: C
     Explanation: First is true; second is false — they don’t require a medium.

 


  1. Assertion: Ultraviolet rays are used in detecting forged documents.
    Reason: UV rays cause certain materials to fluoresce.
     Answer: A
     Explanation: Both true and correctly linked.

 


  1. Assertion: Tyndall Effect is used to detect particle size in colloids.
    Reason: Colloidal particles scatter light.
     Answer: A
     Explanation: Both statements are true and correctly linked.

 


  1. Assertion: Infrared radiation is invisible.
    Reason: Its wavelength is longer than red light.
     Answer: A
     Explanation: Both statements are true and related.

 


  1. Assertion: Visible light is a part of electromagnetic spectrum.
    Reason: It can be detected by the human eye.
     Answer: A
     Explanation: Both true and reason supports assertion.

 


  1. Assertion: Gamma rays are used in radio broadcasting.
    Reason: They have very high penetration power.
     Answer: C
     Explanation: Gamma rays are not used in radio.

 


  1. Assertion: UV rays do not pass through glass.
    Reason: Glass absorbs ultraviolet radiation.
     Answer: A
     Explanation: Both are true and related.

 


  1. Assertion: Wavelength and frequency are directly proportional.
    Reason: As frequency increases, wavelength increases.
     Answer: D
     Explanation: They are inversely proportional.

 


  1. Assertion: Radio waves have the longest wavelength.
    Reason: They are used in TV and radio transmission.
     Answer: A
     Explanation: Both true and reason is correct.

 


  1. Assertion: Infrared radiation is used in night-vision devices.
    Reason: It is emitted by all warm objects.
     Answer: A
     Explanation: Both are correct and related.

 


  1. Assertion: Electromagnetic waves transfer energy.
    Reason: They require a medium for propagation.
     Answer: C
     Explanation: They do transfer energy, but don’t require a medium.

 


  1. Assertion: Red light scatters least in the atmosphere.
    Reason: It has the longest wavelength among visible colours.
     Answer: A
     Explanation: Both are true and correctly related.

 


  1. Assertion: Scattering of light depends on the size of particles.
    Reason: Smaller particles scatter longer wavelengths more.
     Answer: C
     Explanation: Smaller particles scatter shorter wavelengths more.

 


  1. Assertion: All EM waves are transverse in nature.
    Reason: They can propagate through vacuum.
     Answer: B
     Explanation: Both are true but reason doesn’t explain transverse nature.

 


  1. Assertion: Dispersion occurs in a prism due to variation in speed of light.
    Reason: Each colour travels at a different speed in glass.
     Answer: A
     Explanation: Both are true and related.

 


  1. Assertion: Tyndall Effect is observed only in solutions.
    Reason: Particles in solution are large enough to scatter light.
     Answer: D
     Explanation: Tyndall Effect occurs in colloids, not true solutions.

 


  1. Assertion: X-rays have longer wavelength than UV rays.
    Reason: They have higher frequency than UV rays.
     Answer: D
     Explanation: Both are false.

 


  1. Assertion: UV radiation is used in air and water purification.
    Reason: It kills bacteria and viruses.
     Answer: A
     Explanation: Both are true and related.

 


  1. Assertion: Blue light has a higher frequency than red light.
    Reason: Frequency is inversely related to wavelength.
     Answer: A
     Explanation: Both are true and correctly linked.

 


  1. Assertion: Electromagnetic spectrum is classified based on wavelength.
    Reason: Different wavelengths have different properties and uses.
     Answer: A
     Explanation: Both true and correctly linked.

 


  1. Assertion: Infrared radiation passes through glass.
    Reason: Glass is transparent to all EM radiations.
     Answer: C
     Explanation: Glass is not transparent to IR; second statement is false.

 


  1. Assertion: X-rays are produced by stopping high-speed electrons.
    Reason: This sudden deceleration produces high-energy photons.
     Answer: A
     Explanation: Both are correct and linked.

 


  1. Assertion: Gamma rays are used in imaging bones.
    Reason: They pass through soft tissue but are absorbed by bones.
     Answer: C
     Explanation: X-rays are used, not gamma rays.

 


  1. Assertion: UV radiation causes fluorescence.
    Reason: It excites electrons in certain substances.
     Answer: A
     Explanation: Both are correct and related.

 


  1. Assertion: Blue light bends the least in a prism.
    Reason: It has the longest wavelength.
     Answer: D
     Explanation: Both statements are false.

 


  1. Assertion: Electromagnetic waves have electric and magnetic components.
    Reason: These components oscillate parallel to each other.
     Answer: C
     Explanation: They oscillate perpendicular to each other.

 


  1. Assertion: Green light has a lower frequency than blue light.
    Reason: It has a longer wavelength than blue light.
     Answer: A
     Explanation: Both are true and related.

 


  1. Assertion: X-rays are visible to the human eye.
    Reason: They have frequencies within the visible range.
     Answer: D
     Explanation: Both statements are false.

 


  1. Assertion: UV rays are more energetic than visible light.
    Reason: They have higher frequency and shorter wavelength.
     Answer: A
     Explanation: Both are correct and related.

 


  1. Assertion: All colours of light travel at the same speed in glass.
    Reason: Glass is a uniform medium.
     Answer: D
     Explanation: Different colours travel at different speeds in glass.

 


  1. Assertion: Microwaves are used in communication.
    Reason: They are reflected by the ionosphere.
     Answer: C
     Explanation: Microwaves pass through the ionosphere, not reflected.

 


  1. Assertion: Blue light is scattered more than red.
    Reason: Scattering is inversely proportional to the fourth power of wavelength.
     Answer: A
     Explanation: Both are true and reason explains assertion.

 


  1. Assertion: Gamma rays have the highest frequency in the EM spectrum.
    Reason: Frequency increases as wavelength decreases.
     Answer: A
     Explanation: Both are true and correctly linked.

True or False

  1. Dispersion is the bending of light when it passes through a prism.
    Answer: False

 

  1. Violet light has a shorter wavelength than red light.
    Answer: True

 

  1. Gamma rays have the longest wavelength in the electromagnetic spectrum.
    Answer: False

 

  1. Infrared radiation can be felt as heat.
    Answer: True

 

  1. Scattering of light is responsible for the blue colour of the sky.
    Answer: True

 

  1. Red light bends more than violet light in a prism.
    Answer: False

 

  1. X-rays can affect photographic plates.
    Answer: True

 

  1. Ultraviolet radiation causes fluorescence in certain substances.
    Answer: True

 

  1. All electromagnetic waves travel at different speeds in vacuum.
    Answer: False

 

  1. A prism produces dispersion due to reflection.
    Answer: False

 

  1. Ultraviolet rays can cause skin cancer.
    Answer: True

 

  1. Visible light ranges from approximately 400 nm to 800 nm.
    Answer: True

 

  1. The spectrum formed by white light is discrete.
    Answer: False

 

  1. Infrared radiation has a frequency higher than that of visible light.
    Answer: False

 

  1. Gamma rays are used in satellite communication.
    Answer: False

 

  1. Tyndall Effect is observed in colloidal substances.
    Answer: True

 

  1. Red light has the highest frequency in the visible spectrum.
    Answer: False

 

  1. Ultraviolet rays can pass through ordinary glass.
    Answer: False

 

  1. Green light has a wavelength range of approximately 495–570 nm.
    Answer: True

 

  1. X-rays are used to treat cancer.
    Answer: False

 

  1. Violet light is scattered more than red light.
    Answer: True

 

  1. A longer wavelength means higher frequency.
    Answer: False

 

  1. Newton discovered the spectrum of white light.
    Answer: True

 

  1. Microwave ovens use ultraviolet rays to heat food.
    Answer: False

 

  1. Gamma rays are highly penetrating and used for medical sterilization.
    Answer: True

 

  1. Red light is visible but infrared radiation is not.
    Answer: True

 

  1. X-rays are not a part of the electromagnetic spectrum.
    Answer: False

 

  1. The speed of all electromagnetic waves in vacuum is 3 × 10⁸ m/s.
    Answer: True

 

  1. Refraction is responsible for the formation of the spectrum in a prism.
    Answer: True

 

  1. Radio waves are used in X-ray imaging.
    Answer: False

 

  1. Ultraviolet rays have less energy than visible light.
    Answer: False

 

  1. The sun appears red during sunrise and sunset due to scattering of shorter wavelengths.
    Answer: True

 

  1. Blue light has a longer wavelength than green light.
    Answer: False

 

  1. The electromagnetic spectrum is arranged in increasing order of frequency.
    Answer: False

 

  1. Microwaves are used in radar and satellite communication.
    Answer: True

 

  1. All colours of visible light travel at the same speed in vacuum.
    Answer: True

 

  1. UV radiation is part of visible light.
    Answer: False

 

  1. A triangular prism produces dispersion due to different refractive indices of colours.
    Answer: True

 

  1. Infrared radiation is commonly used in night vision cameras.
    Answer: True

 

  1. Frequency and wavelength are inversely related.
    Answer: True

 

  1. The angle of deviation is always the same for all colours in a prism.
    Answer: False

 

  1. Green light has higher frequency than blue light.
    Answer: False

 

  1. Tyndall Effect is a result of light scattering by large particles.
    Answer: False

 

  1. Infrared radiation cannot pass through rock salt.
    Answer: False

 

  1. UV rays can pass through quartz but not through ordinary glass.
    Answer: True

 

  1. The visible spectrum includes UV and IR.
    Answer: False

 

  1. Radio waves have the highest wavelength in the electromagnetic spectrum.
    Answer: True

 

  1. The prism bends red light more than violet light.
    Answer: False

 

  1. Scattering is more effective for shorter wavelengths.
    Answer: True

 

  1. The order of EM waves by increasing wavelength is: Gamma → X-ray → UV → Visible → IR → Microwave → Radio.
    Answer: True

Long Answer Questions

  1. Explain the phenomenon of dispersion of white light through a prism.
    Answer: Dispersion is the phenomenon where white light splits into its component colours (VIBGYOR) when passed through a triangular glass prism. This occurs because different colours of light have different wavelengths and hence different refractive indices in the prism material. As a result, each colour bends by a different amount, with violet bending the most and red the least, forming a continuous spectrum.

 

  1. What is the electromagnetic spectrum? Explain its classification.
    Answer: The electromagnetic spectrum is the range of all types of electromagnetic radiation arranged in the order of increasing wavelength or decreasing frequency. It includes, in order: Gamma rays, X-rays, Ultraviolet (UV) rays, Visible light, Infrared (IR) rays, Microwaves, and Radio waves. Each has unique properties and applications based on its energy, wavelength, and frequency.

 

  1. Why does violet light bend more than red light in a prism?
    Answer: Violet light bends more than red light in a prism because it has a shorter wavelength and a higher refractive index. As light enters the prism, the amount of bending depends on its wavelength — the shorter the wavelength, the greater the refraction. Hence, violet is deviated the most and red the least.

 

  1. What are the uses of different types of electromagnetic waves?
    Answer: Gamma rays are used in cancer treatment; X-rays are used in medical imaging; UV rays are used in sterilization and detecting forged documents; Visible light enables vision and photography; IR rays are used in thermal imaging and remote controls; Microwaves are used in cooking and satellite communication; Radio waves are used in broadcasting and navigation.

 

  1. Describe the process of formation of a spectrum using a triangular prism.
    Answer: When a beam of white light enters a triangular prism, it slows down and bends due to refraction. Since each colour in white light has a different wavelength, each bends at a different angle. This causes the white light to spread out into its seven constituent colours — violet to red — forming a spectrum on the opposite side of the prism.

 

  1. What is scattering of light? Give examples.
    Answer: Scattering of light is the deviation of light rays from their straight path due to irregularities or particles in the medium. It depends on the wavelength of the light and the size of the particles. Examples include the blue colour of the sky and the reddish appearance of the sun during sunrise and sunset.

 

  1. Explain the Tyndall Effect with an example.
    Answer: The Tyndall Effect is the scattering of light by particles in a colloid or a very fine suspension. When a beam of light passes through such a medium, the light is scattered, making the path of the beam visible. An example is the visibility of sunlight through mist or smoke.

 

  1. Write the differences between ultraviolet, visible, and infrared radiation.
    Answer: Ultraviolet radiation has a wavelength range of 100 Å to 4000 Å, is invisible, causes chemical effects and fluorescence, and can cause skin damage. Visible light ranges from 4000 Å to 8000 Å, is visible to the human eye, and enables vision. Infrared radiation ranges from 8000 Å to 10⁷ Å, is invisible, has strong heating effects, and is used in thermal devices.

 

  1. Why is the sky blue and the sunset red?
    Answer: The sky appears blue due to the scattering of shorter wavelengths like blue by atmospheric molecules (Rayleigh scattering). During sunrise and sunset, the sun’s light travels a longer path through the atmosphere, scattering the shorter wavelengths and allowing only the longer red wavelengths to reach the observer.

 

  1. Describe the properties and uses of infrared radiation.
    Answer: Infrared radiation has a longer wavelength than visible light and is invisible to the human eye. It produces a heating effect, can pass through materials like rock salt, and is absorbed by the skin. It is used in remote controls, thermal imaging, night vision devices, and detecting heat leaks.

 

  1. State the order of electromagnetic waves in increasing wavelength.
    Answer: The electromagnetic waves in order of increasing wavelength are: Gamma rays, X-rays, Ultraviolet rays, Visible light, Infrared rays, Microwaves, and Radio waves. This order also represents decreasing frequency and energy.

 

  1. What are the properties and applications of ultraviolet radiation?
    Answer: Ultraviolet radiation is invisible, has shorter wavelengths than visible light, and carries more energy. It causes fluorescence, affects photographic plates, and is harmful to human skin in high doses. It is used in sterilization, detecting counterfeit notes, and in forensic investigations.

 

  1. What is the significance of wavelength and frequency in electromagnetic waves?
    Answer: Wavelength is the distance between two successive crests or troughs of a wave, and frequency is the number of oscillations per second. They are inversely related — as wavelength increases, frequency decreases. These parameters determine the energy and behavior of electromagnetic waves.

 

  1. How is a continuous spectrum formed through a prism?
    Answer: A continuous spectrum is formed when white light passes through a prism and is dispersed into a seamless band of seven colours (VIBGYOR). This occurs due to the varying degrees of refraction experienced by each colour as they travel through the prism.

 

  1. Explain the health hazards of ultraviolet radiation.
    Answer: Ultraviolet radiation can cause skin burns, premature aging, and increase the risk of skin cancer with prolonged exposure. It can also damage the eyes, causing conditions like cataracts. Protective measures like UV-blocking lenses and sunscreen are recommended.

 

  1. How do infrared and ultraviolet rays differ in their effects and uses?
    Answer: Infrared rays produce heat and are used in heating devices, remote controls, and night vision, while ultraviolet rays are more energetic, can cause chemical effects and skin damage, and are used in sterilization, forensic testing, and security.

 

  1. Describe the scattering of light and its dependency on wavelength.
    Answer: Scattering of light depends on the wavelength of light and the size of the scattering particles. Shorter wavelengths (like blue) are scattered more than longer wavelengths (like red), which is why the sky appears blue and sunsets appear red.

 

  1. Why does white light produce a spectrum but monochromatic light does not?
    Answer: White light consists of multiple wavelengths, each bending at a different angle when passing through a prism, resulting in dispersion and a spectrum. Monochromatic light has only one wavelength, so it does not split and hence no spectrum is formed.

 

  1. What is the effect of a prism on different colours of light?
    Answer: A prism refracts each colour in white light by a different amount due to differences in their wavelengths. Violet is refracted the most, and red the least, resulting in the separation of colours into a spectrum.

 

  1. What are the common features of all electromagnetic waves?
    Answer: All electromagnetic waves are transverse, travel at the speed of light in a vacuum (3 × 10⁸ m/s), do not require a medium, and consist of oscillating electric and magnetic fields perpendicular to each other and to the direction of propagation.

 

  1. Explain the significance of Roentgen’s discovery in medical science.
    Answer: Roentgen discovered X-rays, which revolutionized medical diagnosis by allowing non-invasive imaging of internal body structures such as bones and tissues. It enabled early detection of fractures, infections, and tumors.

 

  1. What happens when white light passes through a glass prism?
    Answer: When white light enters a prism, it is refracted due to the change in medium. Different colours bend by different amounts due to varying wavelengths, leading to dispersion and the formation of a visible spectrum on the other side.

 

  1. How is the electromagnetic spectrum useful in daily life?
    Answer: The electromagnetic spectrum is used in various applications: radio waves in broadcasting, microwaves in cooking, infrared in thermal imaging, visible light in vision, ultraviolet in sterilization, X-rays in diagnostics, and gamma rays in cancer therapy.

 

  1. Compare the wavelengths and energies of red and violet light.
    Answer: Red light has a longer wavelength (~620–750 nm) and lower energy, while violet light has a shorter wavelength (~380–450 nm) and higher energy. This difference affects their refraction and scattering properties.

 

  1. What are the harmful effects of exposure to gamma rays?
    Answer: Gamma rays can penetrate living tissues deeply and cause ionization, damaging DNA and leading to mutations, cancer, or radiation sickness with prolonged exposure. Hence, they are used carefully under controlled medical settings.

 

  1. What are X-rays and how are they used?
    Answer: X-rays are high-energy electromagnetic waves with short wavelengths that can penetrate soft tissues but are absorbed by denser materials like bones. They are used in medical imaging to detect fractures, infections, and dental issues, and in security scanners to inspect luggage.

 

  1. Describe the characteristics of ultraviolet radiation.
    Answer: Ultraviolet radiation is invisible, has a wavelength range of 100 Å to 4000 Å, and is more energetic than visible light. It causes fluorescence, has chemical effects, and can be harmful to the skin. It is used in sterilization, counterfeit detection, and forensic science.

 

  1. Why does a prism produce a spectrum but a rectangular glass slab does not?
    Answer: A prism causes different colours to emerge at different angles due to its non-parallel sides and unequal refraction, resulting in dispersion and a spectrum. A rectangular glass slab has parallel sides, so light emerging from it is not spread into different colours.

 

  1. How are electromagnetic waves produced?
    Answer: Electromagnetic waves are produced by the acceleration or deceleration of charged particles, which generates oscillating electric and magnetic fields that propagate perpendicular to each other and to the direction of wave travel.

 

  1. What is the role of infrared radiation in night vision devices?
    Answer: Night vision devices detect the infrared radiation emitted by warm objects in the dark. These devices convert IR radiation into electronic signals and display thermal images, allowing visibility in low-light conditions.

 

  1. How does the wavelength of EM waves affect their application?
    Answer: The wavelength determines the energy and penetrating ability of EM waves. Shorter wavelengths (e.g., gamma rays) are highly energetic and used in medical treatments, while longer wavelengths (e.g., radio waves) are less energetic and used in communication.

 

  1. Discuss the dangers of overexposure to electromagnetic radiation.
    Answer: Overexposure to high-energy EM radiation like UV, X-rays, or gamma rays can cause cell damage, DNA mutations, burns, cancer, and radiation sickness. Even low-energy waves like microwaves can cause tissue heating with prolonged exposure.

 

  1. Describe how a photodiode responds to different types of radiation.
    Answer: A photodiode converts light into electric current when exposed to radiation. It is sensitive to visible and near-infrared light and can be designed to respond to UV rays. The amount of current generated depends on the intensity and wavelength of the incident radiation.

 

  1. What is meant by a continuous spectrum?
    Answer: A continuous spectrum contains all wavelengths or colours without any gaps, as produced by the dispersion of white light through a prism. It includes the entire visible range from violet to red and is typical of natural sunlight.

 

  1. Explain why ultraviolet radiation is more harmful than infrared radiation.
    Answer: Ultraviolet radiation has higher energy and can penetrate cells, causing damage to DNA and tissues, leading to skin cancer and eye problems. Infrared radiation mainly causes heating and does not have ionizing properties, making it less harmful.

 

  1. How does wavelength affect the scattering of light in the atmosphere?
    Answer: Shorter wavelengths like blue and violet are scattered more by air molecules than longer wavelengths like red. This differential scattering makes the sky appear blue and explains the red/orange hues of the sunrise and sunset.

 

  1. Describe the structure and function of a spectrometer.
    Answer: A spectrometer consists of a collimator, prism, and telescope. It is used to study the spectrum of light by producing and analyzing the dispersion of light into its constituent colours. It helps determine wavelength, refractive index, and spectral lines.

 

  1. What is meant by the term ‘ionizing radiation’?
    Answer: Ionizing radiation has enough energy to remove tightly bound electrons from atoms, creating ions. Gamma rays, X-rays, and some UV rays are ionizing. They are used in cancer treatment and sterilization but are also harmful to living tissue.

 

  1. Why are infrared waves used in burglar alarms?
    Answer: Infrared waves are used in burglar alarms because they can detect heat emitted by human bodies. The alarm is triggered when the IR sensors detect sudden changes in infrared radiation caused by movement in a monitored area.

 

  1. How does the human eye perceive different colours in the visible spectrum?
    Answer: The human eye contains cone cells that are sensitive to different wavelengths of light corresponding to red, green, and blue. The brain interprets the combination of signals from these cells to perceive a full range of colours in the visible spectrum.

 

  1. What is the relationship between energy, frequency, and wavelength of EM waves?
    Answer: The energy of EM waves is directly proportional to their frequency and inversely proportional to their wavelength. Higher frequency waves (like gamma rays) have more energy, and longer wavelength waves (like radio waves) have less energy.

 

  1. Why are red lights used in traffic signals and warning signs?
    Answer: Red light has the longest wavelength, scatters the least, and is visible from the farthest distance. This makes it suitable for attracting attention and indicating caution or danger in traffic signals and warning signs.

 

  1. What is meant by fluorescence, and which EM wave causes it?
    Answer: Fluorescence is the emission of visible light by a substance that has absorbed ultraviolet radiation. When UV rays excite electrons in the substance, they jump to higher energy levels and release visible light as they return to their original state.

 

  1. Explain the use of electromagnetic radiation in forensic science.
    Answer: Forensic experts use UV radiation to detect body fluids, fingerprints, and forged documents through fluorescence. IR imaging helps detect concealed objects, and X-rays are used for analyzing the contents of sealed packages or containers.

 

  1. Describe how gamma rays are produced and their application in medicine.
    Answer: Gamma rays are produced by radioactive decay of atomic nuclei. In medicine, they are used in radiotherapy to kill cancerous cells because of their high energy and deep penetration, allowing them to destroy tumour tissues with precision.

 

  1. How are microwaves used in daily life?
    Answer: Microwaves are used in cooking (microwave ovens), mobile communication, radar systems, and satellite transmission. They penetrate food and cause water molecules to vibrate, generating heat for quick and uniform cooking.

 

  1. Explain why X-rays are suitable for medical imaging.
    Answer: X-rays can penetrate soft tissues but are absorbed by dense materials like bones. This differential absorption creates contrast on photographic films or digital detectors, making it easy to diagnose fractures, infections, and foreign objects inside the body.

 

  1. How does the energy of an EM wave depend on its frequency?
    Answer: The energy (E) of an electromagnetic wave is directly proportional to its frequency (f), given by the equation E = hf, where h is Planck’s constant. Thus, higher frequency waves carry more energy.

 

  1. Why are radio waves suitable for long-distance communication?
    Answer: Radio waves have long wavelengths and low frequencies, which allow them to diffract around obstacles, reflect off the ionosphere, and travel long distances without significant attenuation.

 

  1. What precautions are taken to protect against harmful electromagnetic radiation?
    Answer: Precautions include using lead shields or aprons during X-ray exposure, applying sunscreen to block UV rays, limiting exposure time, maintaining safe distances from strong radiation sources, and using protective goggles or screens in industrial environments.

Give Reasons

  1. Give reason: White light splits into different colours when passed through a prism.
    Answer: Because each colour has a different wavelength and refractive index, causing unequal bending (refraction) through the prism, resulting in dispersion.

 

  1. Give reason: Violet light deviates more than red light in a prism.
    Answer: Violet has a shorter wavelength and higher refractive index, so it bends more than red light.

 

  1. Give reason: The sky appears blue on a clear day.
    Answer: Because blue light is scattered more than other colours due to its shorter wavelength.

 

  1. Give reason: Sun appears red during sunrise and sunset.
    Answer: Because the sunlight travels a longer path through the atmosphere, and shorter wavelengths are scattered away, leaving red light.

 

  1. Give reason: A spectrum is not formed when monochromatic light passes through a prism.
    Answer: Because monochromatic light contains only one wavelength and does not undergo dispersion.

 

  1. Give reason: A rectangular glass slab does not produce a spectrum.
    Answer: Because the emergent ray is parallel to the incident ray, and all colours undergo equal deviation, preventing dispersion.

 

  1. Give reason: Ultraviolet rays can cause skin damage.
    Answer: Because they have high energy and can penetrate the skin, damaging cells and DNA.

 

  1. Give reason: Infrared rays are used in remote controls.
    Answer: Because they can transmit signals invisibly and are easily detected by sensors.

 

  1. Give reason: Red light is used in danger signals.
    Answer: Because red light has the longest wavelength, scatters the least, and is visible from a distance.

 

  1. Give reason: Gamma rays are used to treat cancer.
    Answer: Because they have very high energy and penetrating power that can destroy cancerous cells.

 

  1. Give reason: Microwave ovens use microwave radiation.
    Answer: Because microwaves can penetrate food and cause water molecules to vibrate, generating heat.

 

  1. Give reason: X-rays are useful in medical diagnostics.
    Answer: Because they penetrate soft tissues but are absorbed by bones, allowing internal imaging.

 

  1. Give reason: The prism disperses light but the lens does not.
    Answer: Because a prism has non-parallel surfaces and causes different wavelengths to refract at different angles, whereas a lens refracts all rays towards a focal point.

 

  1. Give reason: Ultraviolet rays are used in sterilization.
    Answer: Because they kill bacteria and viruses by damaging their DNA.

 

  1. Give reason: Infrared rays are used in thermal imaging.
    Answer: Because they detect heat emitted by objects and convert it into images.

 

  1. Give reason: Scattering is more effective for shorter wavelengths.
    Answer: Because shorter wavelengths are deflected more by air molecules than longer wavelengths.

 

  1. Give reason: Glass blocks ultraviolet radiation but quartz does not.
    Answer: Because glass absorbs UV rays, while quartz is transparent to UV rays.

 

  1. Give reason: Red light appears at the top and violet at the bottom of the spectrum.
    Answer: Because red deviates the least and violet deviates the most due to differences in refractive indices.

 

  1. Give reason: Electromagnetic waves can travel through vacuum.
    Answer: Because they do not require a medium and are formed by oscillating electric and magnetic fields.

 

  1. Give reason: The sun emits a continuous spectrum.
    Answer: Because it emits all wavelengths of visible light due to its high temperature.

 

  1. Give reason: A spectrometer is used to study light spectra.
    Answer: Because it can accurately measure angles of deviation and refractive indices of different colours.

 

  1. Give reason: Infrared radiation is felt as heat.
    Answer: Because it causes molecules in objects to vibrate, producing thermal energy.

 

  1. Give reason: UV radiation is harmful to the eyes.
    Answer: Because it can damage the cornea and lens, leading to cataracts or blindness.

 

  1. Give reason: Radio waves can travel long distances.
    Answer: Because of their long wavelengths, they can diffract around obstacles and reflect off the ionosphere.

 

  1. Give reason: We cannot see ultraviolet or infrared radiation.
    Answer: Because their wavelengths fall outside the visible range of the human eye.

 

  1. Give reason: Gamma rays are used in food irradiation.
    Answer: Because they destroy bacteria and parasites without raising temperature.

 

  1. Give reason: Fluorescent materials glow under UV light.
    Answer: Because they absorb UV radiation and re-emit it as visible light.

 

  1. Give reason: Green light is refracted more than red but less than violet.
    Answer: Because its wavelength is intermediate, so its refractive index lies between that of red and violet.

 

  1. Give reason: X-rays are not used in microwave ovens.
    Answer: Because they are too energetic and dangerous for food heating purposes.

 

  1. Give reason: Microwaves are used in radar systems.
    Answer: Because they can detect objects and reflect back with measurable time delays.

 

  1. Give reason: Only certain electromagnetic waves are visible.
    Answer: Because only wavelengths between 400–800 nm stimulate the photoreceptors in the human eye.

 

  1. Give reason: Photographic plates are affected by ultraviolet rays.
    Answer: Because UV rays have sufficient energy to cause chemical changes on the plates.

 

  1. Give reason: The spectrum produced by a prism is continuous.
    Answer: Because white light contains all wavelengths blended without gaps.

 

  1. Give reason: Infrared rays are used in TV remotes instead of visible light.
    Answer: Because they are invisible and do not interfere with the viewing experience.

 

  1. Give reason: Blue light scatters more than red light.
    Answer: Because it has a shorter wavelength, which increases its interaction with air particles.

 

  1. Give reason: Ultraviolet rays are filtered in sunglasses.
    Answer: Because they can harm the retina and cause eye damage with prolonged exposure.

 

  1. Give reason: Different colours have different speeds in glass.
    Answer: Because the refractive index of glass varies for different wavelengths.

 

  1. Give reason: UV rays are used in forensic science.
    Answer: Because they make invisible stains and substances fluoresce, aiding investigation.

 

  1. Give reason: Gamma rays are dangerous to living tissues.
    Answer: Because they are highly penetrating and ionize biological molecules.

 

  1. Give reason: Infrared waves are used in automatic door sensors.
    Answer: Because they detect the presence of heat from a person approaching the door.

 

  1. Give reason: X-ray operators use lead shields.
    Answer: Because lead blocks X-rays and protects the body from radiation exposure.

 

  1. Give reason: Microwaves can cook food faster.
    Answer: Because they cause rapid vibration of water molecules, generating internal heat quickly.

 

  1. Give reason: A pencil appears bent in a glass of water.
    Answer: Because of refraction — light changes direction as it passes between air and water.

 

  1. Give reason: Glass is transparent to visible light.
    Answer: Because visible light passes through glass with minimal absorption or scattering.

 

  1. Give reason: Gamma rays are used in nuclear medicine.
    Answer: Because they provide high-resolution imaging and can destroy specific cells.

 

  1. Give reason: The sun’s light contains infrared radiation.
    Answer: Because the sun emits a wide spectrum of radiation, including infrared.

 

  1. Give reason: Scientists wear protective suits when working with radiation.
    Answer: To shield themselves from harmful ionizing radiation that can damage tissues.

 

  1. Give reason: Glass is opaque to ultraviolet rays.
    Answer: Because UV rays are absorbed by the molecular structure of glass.

 

  1. Give reason: The colour of an object depends on the light it reflects.
    Answer: Because we perceive only the wavelengths that are reflected by the object’s surface.

 

  1. Give reason: EM waves do not need a medium to travel.
    Answer: Because they are oscillations of electric and magnetic fields that can propagate through a vacuum.

Arrange the Words 

Case Studies

  1. Case Study:
    A forensic expert shines an invisible beam on a blood-stained cloth and the blood glows brightly in a dark room.
    Question: Which type of radiation is being used?
     Answer: Ultraviolet radiation

 

  1. Case Study:
    A doctor uses a special machine to look at a patient’s fractured bone without any surgery.
    Question: What type of electromagnetic radiation is being used?
     Answer: X-rays

 

  1. Case Study:
    During a hot day, a black shirt feels much warmer than a white one.
    Question: Which type of EM wave is responsible for the heating?
     Answer: Infrared radiation

 

  1. Case Study:
    At sunset, the sun appears deep red as it approaches the horizon.
    Question: Which phenomenon causes this effect?
     Answer: Scattering of shorter wavelengths

 

  1. Case Study:
    A police officer uses a night vision device to locate a suspect in total darkness.
    Question: Which type of radiation helps in night vision?
     Answer: Infrared radiation

 

  1. Case Study:
    In a science lab, white light is passed through a prism and seven colours appear on the screen.
    Question: What phenomenon is responsible for this effect?
     Answer: Dispersion of light

 

  1. Case Study:
    Astronomers study distant stars and galaxies using radiation that passes through space without any medium.
    Question: What type of wave is used in such observations?
     Answer: Electromagnetic waves

 

  1. Case Study:
    In a hospital, gamma radiation is used to destroy cancerous cells in a patient’s body.
    Question: Why is gamma radiation suitable for this purpose?
     Answer: Because it has high energy and strong penetration to destroy malignant cells

 

  1. Case Study:
    A student holds a triangular prism in sunlight and sees a rainbow-like band of colours on a wall.
    Question: What is this band of colours called?
     Answer: Spectrum

 

  1. Case Study:
    An engineer designs a remote control that works using invisible light.
    Question: What kind of EM radiation does the remote use?
     Answer: Infrared radiation

 

  1. Case Study:
    An airport security officer uses a scanning machine to detect objects hidden inside luggage.
    Question: Which radiation allows the scanner to see through the bags?
     Answer: X-rays

 

  1. Case Study:
    After turning on the microwave oven, food heats up quickly from inside.
    Question: What type of wave is used in a microwave oven?
     Answer: Microwaves

 

  1. Case Study:
    A laboratory experiment requires the study of different wavelengths of light. A device is used to measure angles and wavelengths.
    Question: Which instrument is most likely being used?
     Answer: Spectrometer

 

  1. Case Study:
    A soldier uses a thermal imaging camera during a night patrol to detect movement in pitch darkness.
    Question: Which EM wave is detected by the thermal camera?
     Answer: Infrared radiation

 

  1. Case Study:
    A student learns that electromagnetic waves can travel through vacuum. She wonders how sunlight reaches Earth.
    Question: Which property of EM waves allows this?
     Answer: They do not require a medium for propagation

 

  1. Case Study:
    A science museum displays a UV cabinet where special security threads in banknotes glow.
    Question: What physical effect is responsible for the glow?
     Answer: Fluorescence under ultraviolet light

 

  1. Case Study:
    While watching fireworks, a child notices different colours in the sky.
    Question: What causes different colours in the fireworks?
     Answer: Different elements emit different wavelengths when excited

 

  1. Case Study:
    During an eclipse, astronomers study the sun’s corona using high-frequency radiation.
    Question: Which type of EM radiation do they use?
     Answer: Ultraviolet and X-rays

 

  1. Case Study:
    In an experiment, a beam of light enters glass from air and changes direction.
    Question: Which phenomenon is responsible for this?
     Answer: Refraction

 

  1. Case Study:
    A student uses a diffraction grating instead of a prism and still sees the spectrum of light.
    Question: Why does a diffraction grating also produce a spectrum?
     Answer: Because it separates light into different wavelengths through interference

Numericals

  1. Calculate the frequency of light of wavelength 600 nm. (Speed of light = 3 × 10⁸ m/s)
    → Frequency (f) = Speed / Wavelength = (3 × 10⁸) / (600 × 10⁻⁹)
    Answer: 5 × 10¹⁴ Hz

 

  1. Find the wavelength of light of frequency 7.5 × 10¹⁴ Hz.
    → Wavelength (λ) = Speed / Frequency = (3 × 10⁸) / (7.5 × 10¹⁴)
    Answer: 4 × 10⁻⁷ m or 400 nm

 

  1. Light has a frequency of 5 × 10¹⁴ Hz. Find its wavelength.
    → λ = 3 × 10⁸ / 5 × 10¹⁴ = 6 × 10⁻⁷ m
    Answer: 600 nm

 

  1. Wavelength = 450 nm. Find frequency.
    → f = 3 × 10⁸ / (450 × 10⁻⁹) = 6.67 × 10¹⁴
    Answer: 6.67 × 10¹⁴ Hz

 

  1. Frequency = 7.5 × 10¹⁴ Hz. Find wavelength.
    → λ = 3 × 10⁸ / 7.5 × 10¹⁴ = 4 × 10⁻⁷ m
    Answer: 400 nm

 

  1. Speed of light in glass = 2 × 10⁸ m/s. Find refractive index.
    → n = c/v = (3 × 10⁸) / (2 × 10⁸)
    Answer: 1.5

 

  1. Refractive index of water = 1.33. Find speed of light in water.
    → v = c/n = (3 × 10⁸) / 1.33
    Answer: 2.26 × 10⁸ m/s

 

  1. Wavelength of red light = 700 nm. Find frequency.
    → f = 3 × 10⁸ / (700 × 10⁻⁹)
    Answer: 4.29 × 10¹⁴ Hz

 

  1. λ = 550 nm. Find frequency.
    → f = 3 × 10⁸ / (550 × 10⁻⁹) = 5.45 × 10¹⁴
    Answer: 5.45 × 10¹⁴ Hz

 

  1. Distance = 1.5 × 10⁸ m, Time = 0.5 s. Find speed.
    → Speed = Distance / Time = 1.5 × 10⁸ / 0.5
    Answer: 3 × 10⁸ m/s

 

  1. Frequency = 2 × 10⁹ Hz. Find wavelength.
    → λ = 3 × 10⁸ / 2 × 10⁹ = 0.15 m
    Answer: 0.15 m

 

  1. Wavelength = 1000 m. Find frequency.
    → f = 3 × 10⁸ / 1000
    Answer: 3 × 10⁵ Hz

 

  1. Speed of light in medium = 2.4 × 10⁸ m/s. Find refractive index.
    → n = 3 × 10⁸ / 2.4 × 10⁸
    Answer: 1.25

 

  1. Frequency = 3.75 × 10¹⁴ Hz. Find wavelength.
    → λ = 3 × 10⁸ / 3.75 × 10¹⁴ = 8 × 10⁻⁷ m
    Answer: 800 nm

 

  1. Time = 4 × 10⁻⁷ s, Distance = 120 m. Find speed.
    → v = d / t = 120 / (4 × 10⁻⁷)
    Answer: 3 × 10⁸ m/s

 

  1. λ = 500 nm, f = 6 × 10¹⁴ Hz. Verify speed.
    → v = f × λ = 6 × 10¹⁴ × 500 × 10⁻⁹
    Answer: 3 × 10⁸ m/s

 

  1. Frequency of X-ray = 3 × 10¹⁸ Hz. Find wavelength.
    → λ = 3 × 10⁸ / 3 × 10¹⁸
    Answer: 1 × 10⁻¹⁰ m

 

  1. What is the speed of gamma rays in vacuum?
    → All EM waves travel at same speed in vacuum
    Answer: 3 × 10⁸ m/s

 

  1. Frequency = 5.1 × 10¹⁴ Hz. Find wavelength.
    → λ = 3 × 10⁸ / 5.1 × 10¹⁴
    Answer: 5.88 × 10⁻⁷ m or 588 nm

 

  1. Distance = 90,000 km = 9 × 10⁷ m. Time = ?
    → t = d / c = 9 × 10⁷ / 3 × 10⁸
    Answer: 0.3 s

 

  1. Refractive index = 1.52. Find speed of light in medium.
    → v = 3 × 10⁸ / 1.52
    Answer: 1.97 × 10⁸ m/s

 

  1. Light travels from air (n = 1) to glass (n = 1.5). Calculate its speed in glass.
    → v = 3 × 10⁸ / 1.5
    Answer: 2 × 10⁸ m/s

 

  1. EM wave frequency = 10¹² Hz. Find its wavelength.
    → λ = 3 × 10⁸ / 10¹²
    Answer: 3 × 10⁻⁴ m

 

  1. Calculate frequency of blue light with wavelength 450 nm.
    → f = 3 × 10⁸ / (450 × 10⁻⁹)
    Answer: 6.67 × 10¹⁴ Hz

 

  1. A signal takes 2 seconds to reach Earth from Mars, 6 × 10⁸ m away. Find speed.
    → v = d / t = 6 × 10⁸ / 2
    Answer: 3 × 10⁸ m/s

 

  1. Refractive index = 1.4, Speed in vacuum = 3 × 10⁸. Find speed in medium.
    → v = 3 × 10⁸ / 1.4
    Answer: 2.14 × 10⁸ m/s

 

  1. Frequency = 2.5 × 10¹⁴ Hz, Wavelength = ?
    → λ = 3 × 10⁸ / 2.5 × 10¹⁴
    Answer: 1.2 × 10⁻⁶ m

 

  1. Calculate wavelength for infrared wave of frequency 3 × 10¹³ Hz.
    → λ = 3 × 10⁸ / 3 × 10¹³
    Answer: 1 × 10⁻⁵ m

 

  1. Wavelength of UV light = 300 nm. Find its frequency.
    → f = 3 × 10⁸ / (300 × 10⁻⁹)
    Answer: 1 × 10¹⁵ Hz

 

  1. Light travels 1.2 × 10⁸ m in 0.4 s. Find speed.
    → v = d / t = 1.2 × 10⁸ / 0.4
    Answer: 3 × 10⁸ m/s

 

  1. Frequency = 6 × 10¹⁴ Hz, λ = ?
    → λ = 3 × 10⁸ / 6 × 10¹⁴
    Answer: 5 × 10⁻⁷ m or 500 nm

 

  1. X-ray has λ = 1 × 10⁻¹⁰ m. Find its frequency.
    → f = 3 × 10⁸ / 1 × 10⁻¹⁰
    Answer: 3 × 10¹⁸ Hz

 

  1. Radio wave λ = 200 m. Find frequency.
    → f = 3 × 10⁸ / 200
    Answer: 1.5 × 10⁶ Hz

 

  1. Frequency = 5 × 10⁶ Hz. Find wavelength.
    → λ = 3 × 10⁸ / 5 × 10⁶
    Answer: 60 m

 

  1. Find refractive index when speed in medium = 2.5 × 10⁸ m/s
    → n = 3 × 10⁸ / 2.5 × 10⁸
    Answer: 1.2

 

  1. If frequency of UV radiation = 1.2 × 10¹⁵ Hz, find λ.
    → λ = 3 × 10⁸ / 1.2 × 10¹⁵
    Answer: 2.5 × 10⁻⁷ m

 

  1. Wavelength = 100 nm. Find frequency.
    → λ = 100 × 10⁻⁹ = 1 × 10⁻⁷ m
    → f = 3 × 10⁸ / 1 × 10⁻⁷
     Answer: 3 × 10¹⁵ Hz

 

  1. How far does light travel in 1 nanosecond?
    → t = 1 ns = 1 × 10⁻⁹ s
    → d = c × t = 3 × 10⁸ × 1 × 10⁻⁹
     Answer: 0.3 m

 

  1. Frequency = 4.5 × 10¹⁴ Hz. Find λ.
    → λ = 3 × 10⁸ / 4.5 × 10¹⁴
    Answer: 6.67 × 10⁻⁷ m

 

  1. A signal with λ = 10 cm. Find frequency.
    → λ = 0.1 m
    → f = 3 × 10⁸ / 0.1
     Answer: 3 × 10⁹ Hz

 

  1. Light travels 30 cm in how much time?
    → d = 0.3 m, t = d / c = 0.3 / (3 × 10⁸)
    Answer: 1 × 10⁻⁹ s

 

  1. Find λ of EM wave with f = 1.5 × 10¹⁵ Hz
    → λ = 3 × 10⁸ / 1.5 × 10¹⁵
    Answer: 2 × 10⁻⁷ m

 

  1. If λ = 650 nm, f = ?
    → f = 3 × 10⁸ / (650 × 10⁻⁹)
    Answer: 4.62 × 10¹⁴ Hz

 

  1. Time = 5 × 10⁻⁹ s, Distance = ?
    → d = c × t = 3 × 10⁸ × 5 × 10⁻⁹
    Answer: 1.5 m

 

  1. Microwave has f = 3 × 10⁹ Hz. Find λ.
    → λ = 3 × 10⁸ / 3 × 10⁹
    Answer: 0.1 m

 

  1. Infrared wave has λ = 1 mm. Find frequency.
    → λ = 1 × 10⁻³ m
    → f = 3 × 10⁸ / 1 × 10⁻³
     Answer: 3 × 10¹¹ Hz

 

  1. Speed of light in medium = 2 × 10⁸ m/s. Refractive index = ?
    → n = 3 × 10⁸ / 2 × 10⁸
    Answer: 1.5

 

  1. λ = 1.2 × 10⁻⁶ m, f = ?
    → f = 3 × 10⁸ / 1.2 × 10⁻⁶
    Answer: 2.5 × 10¹⁴ Hz

 

  1. How long does light take to travel 60 m?
    → t = 60 / 3 × 10⁸
    Answer: 2 × 10⁻⁷ s

 

  1. UV light has f = 8 × 10¹⁴ Hz. λ = ?
    → λ = 3 × 10⁸ / 8 × 10¹⁴
    Answer: 3.75 × 10⁻⁷ m

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