The electric field of a plane electromagnetic wave is given by E → = E 0 i ^ c o s k z c o s ( ω t ) The corresponding magnetic field B → is then given by:

B → = E 0 c j ^ sin ⁡ k z s i n ( ω t )

B → = E 0 c j ^ cos ⁡ k z s i n ( ω t )

B → = E 0 c k ^ sin ⁡ k z c o s ( ω t )

B → = E 0 c j ^ sin ⁡ k z c o s ( ω t )

EASY

Earn 100

The average force exerted on the surface is directly proportional to the total momentum delivered to that surface for complete absorption.

100% studentsanswered this correctly

Important Questions on Electromagnetic Waves

MEDIUM

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

Sunlight of intensity

50 W m^{- 2}

is incident normally on the surface of a solar panel. Some part of incident energy (

25 %

) is reflected from the surface and the rest is absorbed. The force exerted on

1 m^{2}

surface area will be close to

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

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

Light with an energy flux of

25 \times 10^{4} {W m}^{- 2}

falls on a perfectly reflecting surface at normal incidence. If the surface area is

15 {c m}^{2},

the average force exerted on the surface is:

MEDIUM

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

The electric field in a plane electromagnetic wave is given by

\vec{E} = 200 \cos [(0.5 \times 10^{3} m^{- 1}) x - (1.5 \times 10^{11} rad s^{- 1}) t] V m^{- 1} \hat{j}

.
If this wave falls normally on a perfectly reflecting surface having an area of

100 {cm}^{2}

. If the radiation pressure exerted by the E.M. wave on the surface during a

10 \min

exposure is

\frac{k}{10^{9}} N m^{- 2}

. Find the value of

k

EASY

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

Write an expression for the speed of light in a material medium of relative permittivity

ε_{r}

and relative magnetic permeability

μ_{r}

EASY

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

Light with an energy flux of

120 W {cm}^{- 2}

falls on a normal reflecting surface at normal incidence. Find the average force exerted on the surface in

20 minutes

if the surface has an area of

2

square meter.

MEDIUM

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

The mass of a hydrogen molecule is

3.32 \times 10^{- 27} kg .

10^{23}

hydrogen molecules strike, per second, a fixed wall of the area

2 {cm}^{2}

at an angle of

45^{o}

to the normal, and rebound elastically with a speed of

10^{3} m s^{- 1},

then the pressure on the wall is nearly:

MEDIUM

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

A point source of light emits isotropically with a power of $200 W$ . The light is incident normally on a perfectly reflecting circular surface of radius $2 cm$ at a distance of $20 m$ from the source. The force exerted by light on the surface is

Speed of light $c = 3 \times 10^{8} m s^{- 1}$

EASY

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

Electromagnetic waves can be deflected by

MEDIUM

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

A radiation of energy

E

falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (

C

= Velocity of light)

MEDIUM

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

A light bulb of power

100 W

is placed at the centre of a hollow sphere of radius

10 cm .

If the

66 %

of the energy is converted into light, then the pressure exerted by the light on the surface of the sphere will be
(Assume the surface of sphere to be perfectly absorbing)

EASY

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

The electric field of a plane electromagnetic wave is given by

\vec{E} = E_{0} \hat{i} c o s (k z) c o s (ω t)

The corresponding magnetic field

\vec{B}

is then given by:

EASY

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

The sound waves after converting into the electric waves are not directly transmitted because:

EASY

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

The radiation produced by a

100 W

bulb has the following property

EASY

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

A laser pointer has an output power of

1 mW

and emits light of wavelength

660 nm

. if the beam from the pointer is incident normally on a perfectly reflecting mirror, the force exerted by the light beam on the mirror will be approximately,

EASY

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

A beam of light with intensity

10^{- 3} N m^{- 2}

and cross sectional area

20 {cm}^{2}

is incident on a fully reflective surface at angle

45 °

. Then the force exerted by the beam on the surface is

MEDIUM

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

Sun light falls normally on a surface of area

36 {cm}^{2}

and exerts an average force of

7.2 \times 10^{- 9} N

within a time period of

20

minutes. Considering a case of complete absorption, the energy flux of incident light is

EASY

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

An electromagnetic wave of intensity

I

is incident on a non-reflecting surface. If

C

is the speed of light in free space, then the ratio

\frac{I}{C}

is same as

MEDIUM

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

What do you understand by the statement, “Electromagnetic waves transport momentum”?

EASY

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

An electromagnetic wave is represented by the electric filed

\vec{E} = E_{0} \hat{n} \sin [ω t + (6 y - 8 z)] .

Taking unit vectors in

x, y

and

z

directions to be

\hat{i}, \hat{j}, \hat{k},

the directions of propagations

\hat{s},

is:

The average force exerted on the surface is directly proportional to the total momentum delivered to that surface for complete absorption.

Important Questions on Electromagnetic Waves

Learn and Prepare for any exam you want !