Q.1 Which of the following is an example of an electromagnetic wave?
Sound wave
Water wave
X-ray
Seismic wave
Explanation - Electromagnetic waves include X-rays, radio waves, microwaves, visible light, etc., and they do not require a medium to propagate.
Correct answer is: X-ray
Q.2 The speed of electromagnetic waves in vacuum is approximately:
3 × 10^6 m/s
3 × 10^8 m/s
3 × 10^10 m/s
3 × 10^5 m/s
Explanation - Electromagnetic waves propagate in vacuum at the speed of light, which is 3 × 10^8 m/s.
Correct answer is: 3 × 10^8 m/s
Q.3 Electromagnetic waves are:
Transverse waves
Longitudinal waves
Both transverse and longitudinal
None of the above
Explanation - Electromagnetic waves have electric and magnetic fields perpendicular to each other and to the direction of propagation, making them transverse.
Correct answer is: Transverse waves
Q.4 Which of the following EM waves has the highest frequency?
Radio waves
Infrared
X-rays
Microwaves
Explanation - Frequency increases as wavelength decreases. X-rays have much shorter wavelengths than radio, microwave, and infrared waves.
Correct answer is: X-rays
Q.5 The energy of an electromagnetic wave is directly proportional to:
Wavelength
Amplitude
Frequency
Speed
Explanation - Energy of a photon of EM wave is E = hν, where ν is frequency, showing direct proportionality.
Correct answer is: Frequency
Q.6 Which component of an EM wave is responsible for producing magnetic effects?
Electric field
Magnetic field
Both electric and magnetic fields
Neither
Explanation - The magnetic component of an EM wave interacts with magnetic materials and produces magnetic effects.
Correct answer is: Magnetic field
Q.7 Electromagnetic waves do not require a medium because:
They are longitudinal
They are transverse
They can propagate in vacuum
They travel slowly
Explanation - EM waves are self-propagating due to oscillating electric and magnetic fields, and thus do not require a medium.
Correct answer is: They can propagate in vacuum
Q.8 The wavelength of visible light lies approximately in the range:
400–700 nm
700–1000 nm
100–400 nm
1–10 nm
Explanation - Visible light corresponds to wavelengths roughly from 400 nm (violet) to 700 nm (red).
Correct answer is: 400–700 nm
Q.9 Which law relates the speed of light to its wavelength and frequency?
Ohm’s law
Maxwell’s equation
c = λν
Faraday’s law
Explanation - The speed of light c is the product of wavelength λ and frequency ν: c = λν.
Correct answer is: c = λν
Q.10 The electric and magnetic fields in an EM wave are always:
Parallel to each other
Perpendicular to each other
At 45° to each other
Opposite in direction
Explanation - In an EM wave, electric and magnetic fields are perpendicular to each other and to the direction of propagation.
Correct answer is: Perpendicular to each other
Q.11 Electromagnetic waves with wavelengths greater than 1 m are called:
Microwaves
Radio waves
Infrared waves
X-rays
Explanation - Radio waves have the longest wavelengths in the EM spectrum, typically greater than 1 m.
Correct answer is: Radio waves
Q.12 The intensity of an EM wave is proportional to:
Amplitude squared
Wavelength
Frequency squared
Speed squared
Explanation - The intensity (energy per unit area per unit time) of an EM wave is proportional to the square of its amplitude.
Correct answer is: Amplitude squared
Q.13 Which EM wave is commonly used in remote controls?
Infrared
Microwave
Ultraviolet
X-ray
Explanation - Remote controls emit infrared waves to transmit signals to devices.
Correct answer is: Infrared
Q.14 Which EM wave is most energetic?
Gamma rays
Visible light
Microwaves
Radio waves
Explanation - Energy of EM waves increases with frequency. Gamma rays have the highest frequency and energy.
Correct answer is: Gamma rays
Q.15 Electromagnetic waves are generated by:
Accelerating charges
Constant charges
Magnetic monopoles
Stationary electrons
Explanation - An accelerating electric charge produces a changing electric and magnetic field, generating EM waves.
Correct answer is: Accelerating charges
Q.16 Radio waves can be reflected by:
Ionosphere
Ocean
Metal
All of the above
Explanation - Long-wave radio signals are reflected by the ionosphere, enabling long-distance communication.
Correct answer is: Ionosphere
Q.17 Which EM waves are used for sterilization of medical equipment?
UV rays
Microwaves
Radio waves
Infrared rays
Explanation - Ultraviolet radiation can destroy bacteria and viruses, making it useful for sterilization.
Correct answer is: UV rays
Q.18 The EM spectrum is arranged according to:
Wavelength
Frequency
Energy
All of the above
Explanation - The EM spectrum can be classified by wavelength, frequency, or energy since these are interrelated.
Correct answer is: All of the above
Q.19 The polarization of an EM wave refers to:
Direction of propagation
Direction of electric field oscillation
Magnetic field strength
Wavelength variation
Explanation - Polarization specifies the orientation of the electric field vector in an EM wave.
Correct answer is: Direction of electric field oscillation
Q.20 Which EM waves are used in radar systems?
Microwaves
Infrared waves
X-rays
Gamma rays
Explanation - Radar systems use microwaves because they can penetrate clouds and detect objects at a distance.
Correct answer is: Microwaves
Q.21 The relationship between electric and magnetic fields in a plane EM wave is described by:
Faraday’s law
Maxwell’s equations
Coulomb’s law
Ampere’s law
Explanation - Maxwell’s equations predict the existence and properties of EM waves and relate E and B fields.
Correct answer is: Maxwell’s equations
Q.22 Which of the following EM waves can cause sunburn?
UV rays
Infrared waves
Microwaves
Radio waves
Explanation - Ultraviolet radiation has enough energy to damage skin cells, causing sunburn.
Correct answer is: UV rays
Q.23 The propagation of EM waves in a vacuum is due to:
Mechanical vibration
Oscillating charges
Magnetic monopoles
Sound
Explanation - Oscillating charges generate changing electric and magnetic fields which propagate as EM waves in vacuum.
Correct answer is: Oscillating charges
Q.24 In an EM wave, the direction of propagation is:
Parallel to E field
Parallel to B field
Perpendicular to both E and B fields
Random
Explanation - EM waves are transverse; the propagation direction is perpendicular to both electric and magnetic fields.
Correct answer is: Perpendicular to both E and B fields
Q.25 Microwaves heat food due to interaction with:
Water molecules
Metal atoms
Plastic molecules
Air molecules
Explanation - Microwaves cause water molecules to vibrate, generating heat that cooks food.
Correct answer is: Water molecules