Match List I (Wavelength range of electromagnetic spectrum) with List II (Method of production of these waves) and select the correct option from the options given below the lists. List I List II (a) 700 nm to 1 mm (i) Vibration of atoms and molecules. (b) 1 nm to 400 nm (ii) Inner shell electrons in atoms moving from one energy level to a lower level. (c) < 10 - 3 nm (iii) Radioactive decay of the nucleus. (d) 1 mm to 0 . 1 m (iv) Magnetron valve.

(a) - (i), (b) - (ii), (c) - (iii), (d) - (iv)

(a) - (iii), (b) - (iv), (c) - (i), (d) - (ii)

(a) - (iv), (b) - (iii), (c) - (ii), (d) - (i)

(a) - (ii), (b) - (iii), (c) - (iv), (d) - (i)

Magnetic field in a plane electromagnetic wave is given by, B → = B 0 sin k x + ω t j ^ T . Expression for corresponding electric field will be: (Where c is speed of light)

E → = B 0 c sin k x + ω t k ^ V m - 1

E → = - B 0 c sin k x + ω t k ^ V m - 1

E → = B 0 c sin k x - ω t k ^ V m - 1

E → = B 0 c sin k x + ω t k ^ V m - 1

The electric field of a plane polarized electromagnetic wave in free space at time t = 0 is given by the expression E → x , y = 10 j ^ c o s 6 x + 8 z . The magnetic field B → x , z , t is given by ( c is the velocity of light.)

1 c 6 k ^ - 8 i ^ c o s 6 x + 8 z - 10 c t

1 c 6 k ^ - 8 i ^ cos 6 x + 8 z + 10 c t

1 c 6 k ^ + 8 i ^ cos 6 x + 8 z - 10 c t

1 c 6 k ^ + 8 i ^ cos 6 x - 8 z + 10 c t

HARD

Earn 100

Using $B = μ_{0} H$ find the ratio $\frac{E_{0}}{H_{0}}$ for a plane electromagnetic wave propagating through a vacuum. Show that it has the dimensions of electric resistance. Show that it has the dimensions of electric resistance. This ratio is a universal constant called the impedance of free space.

Important Questions on Electromagnetic Waves

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

Out of the following options which one can be used to produce a propagating electromagnetic wave?

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

A radio transmitter sends out

60 W

of radiation. Assuming that the radiation is uniform on a sphere with the transmitter at its centre, the intensity

(i n W / m^{2})

of the wave at a distance

12 k m

HARD

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

The electric field component of a monochromatic radiation is given by

\vec{E} = 2 E_{0} \cos k z \cos ω t \hat{i}

, Its magnetic field

\vec{B}

is then given by:

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

During the propagation of electromagnetic wave in a particular medium :-

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

The magnetic field in a travelling electromagnetic wave has a peak value of

20 nT

. The peak value of electric field strength is :

HARD

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

Match List I (Wavelength range of electromagnetic spectrum) with List II (Method of production of these waves) and select the correct option from the options given below the lists.

	List I		List II
(a)	$700 nm$ to $1 mm$	(i)	Vibration of atoms and molecules.
(b)	$1 nm$ to $400 nm$	(ii)	Inner shell electrons in atoms moving from one energy level to a lower level.
(c)	$< 10^{- 3} nm$	(iii)	Radioactive decay of the nucleus.
(d)	$1 mm$ to $0.1 m$	(iv)	Magnetron valve.

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

Magnetic field in a plane electromagnetic wave is given by,

\vec{B} = B_{0} \sin (k x + ω t) \hat{j} T

. Expression for corresponding electric field will be:

(Where

c

is speed of light)

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

An EM wave from air enters a medium. The electric fields are

{\vec{E}}_{1} = E_{01} \hat{x} \cos [2 π v (\frac{z}{c} - t)]

in air and

{\vec{E}}_{2} = E_{02} \hat{x} \cos [k (2 z - c t)]

in medium, where the wave number k and frequency

v

refer to their values in the air. The medium is non-magnetic. If

ϵ_{r_{1}}

and

ϵ_{r_{2}}

refer to relative permittivities of air and medium respectively, which of the following options, is correct?

HARD

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

The electric field of a plane polarized electromagnetic wave in free space at time

t = 0

is given by the expression

\vec{E} (x, y) = 10 \hat{j} c o s (6 x + 8 z)

. The magnetic field

\vec{B} (x, z, t)

is given by (

c

is the velocity of light.)

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

An electromagnetic wave travelling in the

x -

direction has frequency of

2 \times 10^{14} H z

and electric field amplitude of

27 V m^{- 1}

oscillates in

Y -

direction. From the options given below, which one describes the magnetic field for this wave?

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

The energy associated with electric field is

(U_{E})

and with magnetic field is

(U_{B})

for an electromagnetic wave in free space. Then:

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

If the magnetic field of a plane electromagnetic wave is given by (The speed of light

= 3 \times 10^{8} m s^{- 1}

)

B = 100 \times 10^{- 6} \sin [2 π \times 2 \times 10^{15} (t - \frac{x}{c})]

then the maximum electric field associated with it is:

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

Match List - I (Electromagnetic wave type) with List - II (Its association/application) and select the correct option from the choices given below the lists :

	List - I		List - II
(a)	Infrared waves	(i)	To treat muscular strain
(b)	Radio waves	(ii)	For broadcasting
(c)	X - rays	(iii)	To detect fracture of bones
(d)	Ultraviolet rays	(iv)	Absorbed by the ozone layer of the atmosphere

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

In an electromagnetic wave in free space the root mean square value of the electric field is

E_{r m s} = 6 V m^{- 1}

. The peak value of the magnetic field is

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

If microwaves,

X ‐

rays, infrared, gamma rays, ultraviolet, radio waves and visible parts of the electromagnetic spectrum are denoted respectively by

M

X

I

G

U

R

and

V

the following is the arrangement in ascending order of the wavelength

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

Consider an electromagnetic wave propagating in vacuum. Choose the correct statement:

EASY

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

Arrange the following electromagnetic radiations per quantum in the order of increasing energy:

A :

Blue light

B :

Yellow light

C :

X-ray

D :

Radiowave

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

For plane electromagnetic waves propagating in the

+ z

-direction, which one of the following combinations gives the correct possible direction for

\vec{E}

and

\vec{B}

field respectively?

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

A red $L E D$ emits light at $0.1 watt$ uniformly around it. The amplitude of the electric field of the light at a distance of $1 m$ from the diode is:

MEDIUM

Physics>Modern Physics>Electromagnetic Waves>Nature of Electromagnetic Waves

The mean intensity of radiation on the surface of the Sun is about

10^{8} W m^{- 2} .

The RMS value of the corresponding magnetic field is closest to:

Using B=μ0H find the ratio E0H0 for a plane electromagnetic wave propagating through a vacuum. Show that it has the dimensions of electric resistance. Show that it has the dimensions of electric resistance. This ratio is a universal constant called the impedance of free space.

Important Questions on Electromagnetic Waves

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