JEE Physics Electromagnetic Waves MCQs

Question. Displacement current is set up between the plates of a capacitor when the potential difference across the plates is
(a) Varying
(b) Minimum
(c) Zero
(d) Maximum

Answer: A

Question. The speed of electromagnetic waves depends upon
(a) Medium, in which it travels
(b) Frequency
(c) Wavelength
(d) Intensity

Answer: A

Question. Electromagnetic wave is deflected by
(a) Neither electric field nor magnetic field
(b) Magnetic field
(c) Electric field
(d) None of these

Answer: A

Question. Red light differs from blue light in its
(a) Frequency
(b) Speed
(c) Intensity
(d) Amplitude

Answer: A

Question. Which of the following has the largest wavelength?
(a) Radio wave
(b) X-ray
(c) Ultraviolet ray
(d) Infra-red ray

Answer: A

Question. Which of the following is incorrect about a plane electromagnetic wave?
The electric field and magnetic field have equal average values
The electric field and magnetic field oscillate in opposite phase
(a) The electric field and magnetic field oscillate in opposite phase
(b) The electric field and magnetic field oscillate in opposite phase
The electric field and magnetic field have equal average values
(c) The electric field and magnetic field both oscillate in same phase
(d) The electric energy and the magnetic energy have equal average values

Answer: B

Question. In a plane electromagnetic wave, which of the following has/ have zero average value in one complete cycle?
(a) Magnetic field (b) Magnetic energy
(c) Electric field (d) Electric energy
(a) (a), (c)
(b) (b), (c)
(c) (a), (d)
(d) All of these

Answer: A

Question. Which of the following represents an infra-red wavelength?
(a) 10^–4 cm
(b) 10^–5 cm
(c) 10^–6 cm
(d) 10^–7 cm

Answer: A

Question. Which of the following is not transported by electromagnetic waves?
(a) Charge
(b) Information
(c) Momentum
(d) Energy

Answer: A

Question. Hertz experiment is used for
(a) Both
(b) Production of electromagnetic wave
(c) Detection of electromagnetic wave
(d) None of these

Answer: A

Question. Electromagnetic waves are produced due to
(a) An accelerated charge
(b) A charge at rest
(c) A moving charge
(d) None of these

Answer: A

Question. Ozone layer blocks the radiation of wavelength
(a) Less than 4 × 10^–7 m
(b) More than 8 × 10^–7m
(c) Between 4 × 10^–7 m to 8 × 10^–7 m
(d) None of these

Answer: A

Question. Which of the following can be used in cancer treatment?
(a) Both
(b) X-rays
(c) Y-rays
(d) UV-rays

Answer: A

Question.  The following can be arranged in decreasing order of wave number
(a) AM radio B. TV and FM radio
(c) Microwave D. Short radio wave
(a) C > D > B > A
(b) A > B > D > C
(c) A > B > C > D
(d) D > C > B > A

Answer: A

Question. Which of the following physical quantities contained in a small volume oscillates at double the frequency of passing electromagnetic wave?
(a) Magnetic energy
(b) All of these
(c) Magnetic field
(d) Electric field

Answer: A

Question. A plane electromagnetic wave of frequency 28 MHz travels in free space along the positive x-direction. At a particular point in space and time, electric field is 9.3 V/m along positive y-direction. The magnetic field (in T) at that point is 
(a) 3.1 × 10^–8 along positive z-direction
(b) 3.2 × 10⁷ along positive z-direction
(c) 3.1 × 10^–8 along negative z-direction
(d) 3.2 × 10⁷ along negative z-direction

Answer: A

Question. The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in vacuum is equal to
(a) Reciprocal of speed of light in vacuum
(b) The speed of light in vacuum
(c) Unity
(d) The ratio of magnetic permeability to the electric susceptibility of vacuum

Answer: A

Question. The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is
(a) Microwaves, infrared, ultraviolet, gamma rays
(b) Microwaves, gamma rays, infrared, ultraviolet
(c) Infrared, microwaves, ultraviolet, gamma rays
(d) Gamma rays, ultraviolet, infrared, microwaves

Answer: A

Question. Which is having minimum wavelength?
(a) Cosmic ray
(b) Ultraviolet rays
(c) X-ray
(d) None of these

Answer: A

Question. What is the cause of “Greenhouse effect”?
(a) Infra-red rays
(b) Ultraviolet rays
(c) X-rays
(d) Radiowaves

Answer: A

Question. Light with an energy flux of 25 × 10⁴ Wm^–2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm², the average force exerted on the surface is
(a) 2.50 × 10^–6 N
(b) 1.25 × 10^–6 N
(c) 1.20 × 10^–6 N
(d) 3.0 × 10^–6 N

Answer: A