CBSE Class 12 Physics Electromagnetic Waves MCQs

Question: The electromagnetic waves do not transport 
(a) energy
(b) charge
(c) momentum
(d) information

Answer: B

Question: The polarisation of electromagnetic wave is in
(a) the directions of electric and magnetic field
(b) the directions of electric field
(c) the direction of magnetic field
(d) can not be polarized

Answer: B

Question: The current in the electric circuit which arises due to flow of electrons in the connecting wires of the circuit in a defined closed path is called
(a) alternating current
(b) direct current
(c) conduction current
(d) displacement current

Answer: C

Question: If a variable frequency ac source connected to a capacitor then with decrease in frequency, the displacement current will
(a) increase
(b) decrease
(c) remain constant
(d) first decrease then increase

Answer: B

Question: Displacement current goes through the gap between the plates of a capacitor when the charge on the capacitor
(a) is changing with time
(b) decreases
(c) does not change
(d) decreases to zero

Answer: A

Question: An electron oscillating with a frequency of 3 × 10⁶ Hz, would generate
(a) X-rays
(b) ultraviolet rays
(c) radio waves
(d) microwaves

Answer: C

Question: Select the wrong statement. EM waves
(a) are transverse in nature.
(b) travel in free space at a speed of light.
(c) are produced by accelerating charges.
(d) travel in all media with same speed.

Answer: D

Question: Which of the following has/have zero average value in a plane electromagnetic wave?
(a) Both magnetic and electric field
(b) Electric field only
(c) Magnetic energy
(d) Electric energy

Answer: A

Question: According to Maxwell’s hypothesis, a changing electric field gives rise to
(a) an e.m.f
(b) electric displacement current
(c) magnetic field
(d) pressure gradient

Answer: C

Question: An electromagnetic wave propagating along north has its electric field vector upwards. Its magnetic field vector point towards
(a) north
(b) east
(c) west
(d) downwards

Answer: B 

Question : The oscillating electric and magnetic vectors of an electromagnetic wave are oriented along
(a) the same direction but differ in phase by 90°
(b) the same direction and are in phase
(c) mutually perpendicular directions and are in phase
(d) mutually perpendicular directions and differ in phase by 90°
Answer: C

Question : Displacement current is
(a) continuous when electric field is changing in the circuit
(b) continuous when magnetic field is changing in the circuit
(c) continuous in both types of fields
(d) continuous through wires and resistance only
Answer: A

Question : In an electromagnetic wave, the electric and magnetic fields are 100 V m^–1 and 0.265 A m^–1. The maximum energy flow is
(a) 26.5 W/m²
(b) 36.5 W/m²
(c) 46.7 W/m²
(d) 765 W/m²
Answer: A

Question : Which of the following electromagnetic waves has the longest wavelength?
(a) uv-rays
(b) Visible light
(c) Radio waves
(d) Microwaves
Answer: B

Question : The range of wavelength of visible light is
(a) 50 Å to 500 Å
(b) 4000 Å to 8000 Å
(c) 9000 Å to 25,000 Å
(d) 15,000 Å to 25,000 Å
Answer: B

Question : The wavelength of X-ray is of the order of
(a) 1 metre
(b) 1 cm
(c) 1 micron
(d) 1 angstrom
Answer: D

Question : Radio waves do not penetrate in the band of
(a) ionosphere
(b) mesosphere
(c) troposphere
(d) stratosphere
Answer: A

Question : What is the cause of “Green house effect”?
(a) Infrared rays
(b) Ultraviolet rays
(c) X-rays
(d) Radio waves
Answer: A

Question : The waves used in telecommunication are
(a) IR
(b) UV
(c) Microwave
(d) Cosmic rays
Answer: C

Question : The electromagnetic radiation used in food processing sterilizing agent is
(a) microwaves
(b) UV rays
(c) gamma rays
(d) radio waves
Answer: B