JEE Physics Electromagnetic Waves MCQs

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: Varying

Question:

• a)

  

• b)

  

• c)

  

• d) 3 i

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d) Zero

Answer:

Question: The speed of electromagnetic waves depends upon

• a) Medium, in which it travels
• b) Frequency
• c) Wavelength
• d) Intensity

Answer: Medium, in which it travels

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Electromagnetic wave is deflected by

• a) Neither electric field nor magnetic field
• b) Magnetic field
• c) Electric field
• d) None of these

Answer: Neither electric field nor magnetic field

Question: Out of the following, choose the ray which does not travel with the velocity of light

• a)

  

• b)

  

• c) Microwave
• d) X-ray

Answer:

Question: Red light differs from blue light in its

• a) Frequency
• b) Speed
• c) Intensity
• d) Amplitude

Answer: Frequency

Question: Which of the following has the largest wavelength?

• a) Radio wave
• b) X-ray
• c) Ultraviolet ray
• d) Infra-red ray

Answer:  Radio wave

Question: Velocity of electromagnetic waves in a medium is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Which of the following is incorrect about a plane electromagnetic wave?

• 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:

The electric field and magnetic field oscillate in opposite phase

The electric field and magnetic field have equal average values

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), (c)

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The speed of electromagnetic wave in a medium (whose dielectric constant is 2.25 and relative permeability is 4) is equal to

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) Radiowave
• b) Microwave
• c) Infrared
• d) Visible light

Answer: Radiowave

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: 10^–4 cm

Question: Which of the following is not transported by electromagnetic waves?

• a) Charge
• b) Information
• c) Momentum
• d) Energy

Answer: Charge

More Questions.......................................

Question: Hertz experiment is used for

• a) Both
• b) Production of electromagnetic wave
• c) Detection of electromagnetic wave
• d) None of these

Answer: Both

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: An accelerated charge

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: Less than 4 × 10^–7 m

Question: Which of the following can be used in cancer treatment?

• a) Both
• b) X-rays
• c) Y-rays
• d) UV-rays

Answer: Both

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: C > D > B > A

Question:

• a) U
• b)

  

• c)

  

• d)

  

Answer: U

Question: 5% of the power of 100 W bulb is converted to visible radiation. Average intensity of visible radiation at a distance of 10 m from the bulb is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: Magnetic energy

Question: A capacitor is connected across a battery which delivers a current of 1 A at an instant in the capacitor. Displacement current through the capacitor at that instant is

• a) 0 A
• b) 1 A
• c) 2 A
• d)

  

Answer: 0 A

Question:

• a) 1 cm
• b) 628 cm
• c) 1.129 cm
• d) 314 cm

Answer: 1 cm

Question:

• a) 2I
• b) I
• c)

  

• d)

  

Answer: 2I

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: 3.1 × 10^–8 along positive z-direction

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: Reciprocal of speed of light in vacuum

Question: The electric and the magnetic field, associated with an e.m. wave, propagating along the +z-axis, can be represented by

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

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: Microwaves, infrared, ultraviolet, gamma rays

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Which of the following electromagnetic radiations have the smallest wavelength?

• a) 

  

• b) X-rays
• c) UV waves
• d) Microwaves

Answer: 

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Which is having minimum wavelength?

• a) Cosmic ray
• b) Ultraviolet rays
• c) X-ray
• d) None of these

Answer: Cosmic ray

Question: What is the cause of “Greenhouse effect”?

• a) Infra-red rays
• b) Ultraviolet rays
• c) X-rays
• d) Radiowaves

Answer: Infra-red rays

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: 2.50 × 10^–6 N

Question:

• a) Moving along x direction with frequency 10⁶ Hz and wavelength 200 m
• b) Moving along x direction with frequency 10⁶ Hz and wavelength 100 m
• c)

  

• d) Moving along x direction with frequency 10⁶ Hz and wavelength 200 m

Answer: Moving along x direction with frequency 10⁶ Hz and wavelength 200 m

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The velocity of electromagnetic wave is parallel to

• a) None of these
• b)

  

• c)

  

• d) Both

Answer: None of these