MCQs of Electromagnetic Waves

Electromagnetic Waves MCQs

MCQs of Electromagnetic Waves

Showing 11 to 20 out of 112 Questions

11.

The frequency of an electromagnetic wave in free space is 2 MHz . When it passes through a region of relative permittivity ε_{r} = 4.0, then its wavelength_____and frequency_____.

(a)	becomes double, becomes half
(b)	becomes double, remains constant
(c)	becomes half , becomes double
(d)	becomes half , remains constant

12.

The rms value of electric field of the radiation coming from the Sun is 720 N/C. The average radiation density is _______ Jm^-3.

(a)	81.35 × 10^-12
(b)	3.3 × 10^-3
(c)	4.58 × 10^-6
(d)	6.37 × 10^-9

13.

In the region closer to the oscillating charges, the phase difference between \vec{E} and \vec{B} fields is______, and their magnitude quickly decreases as_____with distance r from the source .

(a)	0, r^-1
(b)	$\frac{π}{2}, r^{- 3}$
(c)	$\frac{π}{2}, r^{- 1}$
(d)	0, r^-3

14.

At large distances from the source, \vec{E} and \vec{B} are in phase and the decrease in their magnitude is comparatively slower with distance r as per_____and these components are called_____components .

(a)	r^-3 , inductive
(b)	r^-1 , radiated
(c)	r^-3 , radiated
(d)	r^-1, inductive

15.

At room temprature, if the relative permittivity of water be 80, and the relative permeability be 0.0222, then the velocity of light in water is _____ m s^-1.

(a)	3 × 10⁸
(b)	2.5 × 10⁸
(c)	2.25 × 10⁸
(d)	3.5 × 10⁸

16.

If the electric field associated with a radiation of frequency 10 MHz is E = 10 \sin (k x - ω t) \frac{mV}{m}, then its energy density is_____J m^{- 3} . (ε_{0} = 8.85 \times 10^{- 12} C^{2} N^{- 1} m^{- 2})

(a)	4.425 × 10^-16
(b)	6.26 × 10^-14
(c)	8.85 × 10^-16
(d)	8.85 × 10^-14

17.

An electromagnetic wave coming from infinity, enters a medium from the vacuum. For this wave _____ is independent of the medium. [will not change in the medium]

(a)	$ω$
(b)	$k$
(c)	$\frac{ω}{k}$
(d)	$λ$

18.

For a radiation of 6 GHz passing through air, the wave number (number of waves) per 1 m length is _____ (1 GHz = 10⁹ Hz).

(a)	3
(b)	5
(c)	20
(d)	30

19.

The intensity of a plane electromagnetic wave with B₀ = 1.0 × 10^-4 T is _______ Wm^-2 ( c = 3 × 10⁸ m s^-1, µ₀ = 4π × 10^-7 NA^-2 )

(a)	2.38 × 10⁶
(b)	1.19 × 10⁶
(c)	6 × 10⁵
(d)	4.76 × 10⁶

20.

Astronomers have found that the electromagnetic waves of wavelength 21 cm are continuously reaching the Earth's surface. The frequency of this radiation is _____ (c = 3 × 10⁸ ms^-1)

(a)	1.43 GHz
(b)	1.43 MHz
(c)	1.43 kHz
(d)	1.43 Hz

Showing 11 to 20 out of 112 Questions