## Class 12 Physics MCQs Electromagnetic Waves for JEE/NEET

Here, you will get Class 12 Physics MCQ of Chapter 8 Electromagnetic Waves for cracking JEE and NEET/AIIMS. By solving these MCQs of Class 12 Physics Chapter 8 Electromagnetic Waves, you will get the confidence to crack JEE or NEET. Practice MCQ Questions for Class 12 Physics with Answers on a daily basis and score well in exams.

## Electromagnetic Waves Class 12 MCQs Questions with Answers

Which of the following laws was modified by Maxwell by introducing the displacement current?
(a) Gauss’s law
(b) Ampere’s law
(c) Biot-Savart’s law
(d).None of these

Electromagnetic waves have a speed of
(a) 3 × 105 kms-1
(b)3 × 106 kms-1
(c) 3 × 107 kms-1
(d) 3 × 108 kms-1

Answer: (a) 3 × 105 kms-1

Which of the following EMW has highest wavelength?
(a) X-ray
(b) ultraviolet rays
(c) infrared rays
(d) microwaves

Who first demonstrated the existence of em waves?
(a) Hertz
(b) Maxwell
(c) Ampere

An EMW of v = 3 MHz passes from vacuum into dielectric medium with permittivity Er = 4, then
(a) Wavelength is doubled and the frequency remains unchanged
(b) Wavelength is doubled and the frequency become half
(c) Wavelength is halved and the frequency remains unchanged
(d) Wavelength and frequency both remain unchanged

Answer: (c) Wavelength is halved and the frequency remains unchanged

The conduction current is same as displacement current when source is
(a) ac only
(b) dc only
(c) either ac or dc
(d) neither dc nor ac

Answer: (c) either ac or dc

The ultra high frequency band of radio waves in electromagnetic wave is used as in
(a) television waves
(b) cellular phone communication
(d) both (a) and (c)

If ue and um arc the electric and magnetic field densities in an electromagnetic wave, then (c is the speed of light)
(a) ue = um
(b) ue = cum
(c) ue = um/c
(d) None of these

Light Year is the unit of
(a) distance
(b) time
(c) energy
(d) intensity of light

Which of the following electromagnetic waves is used in medicine to destroy cancer cells?
(a) IR-rays
(b) Visible rays
(c) Gamma rays
(d) Ultraviolet rays

Which basic oscillatory circuit is used these days to produce electromagnetic waves?
(a) LC oscillatory circuit
(b) LCR circuit
(c) Inductive circuit
(d) Capacitive circuit

Choose the wave relevant to telecommunication
(a) ultraviolet
(b) infrared
(c) microwave
(d) visible light

Displacement current is always
(a) equal to conduction current
(b) less than conduction current
(c) greater than conduction current
(d) the sum of current due to flow of positive and negative ions

Answer: (a) equal to conduction current

The dimensions of E/Bare same as that of
(a) charge
(b) current
(c) velocity
(d) acceleration

An EMW of v = 3 MHz passes from vacuum into dielectric medium with permittivity Er = 4, then
(a) Wavelength is doubled and the frequency remains unchanged
(b) Wavelength is doubled and the frequency become half
(c) Wavelength is halved and the frequency remains unchanged
(d) Wavelength and frequency both remain unchanged

Answer: (c) Wavelength is halved and the frequency remains unchanged

Frequency of a wave is 6 × 1015. Hz. The wave is
(b) Microwave
(c) X-ray
(d) Ultra violet

(a) transverse EMW
(b) longitudinal EMW
(c) both (a) and (b)
(d) None of these

What physical quantity is the same for X-rays of wavelength 10-10 m, red light of wavelength 680 nm and radio waves of wavelength 500 m?
(a) Wavelength
(b) Frequency
(c) Speed
(d) None of these.

What is the ratio of the speed of infrared and ultraviolet rays in a vacuum?
(a) 1:5
(b) 2:1
(c) 1
(d) 0

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

A charged particle oscillates about its mean equilibrium position with a frequency of 109 Hz. The frequency of electromagnetic waves produced by the oscillator is
(a) 106 Hz
(b) 107 Hz
(c) 108 Hz
(d) 109 Hz

The waves used by artificial satellites for communication is
(a) microwaves
(b) infrared waves
(d) X-rays

Displacement current is due to
(a) the flow of electrons
(b) the Varying electric field
(c) the ionization of atmosphere
(d) the flow of protons

Answer: (b) the Varying electric field

EMW are produced by
(a) charge in uniform motion only
(b) charge at rest only
(c) accelerated or decelerated charge only
(d) all of the above

Answer: (c) accelerated or decelerated charge only

Name the law which states that a varying electric field produces a magnetic field
(a) Biot-Savart’s law