Electromagnetic Waves

An electromagnetic wave travelling in a lossless dielectric medium having a dielectric constant, r = 9, has the electric field, Ex = E0 (kz - 2 106t) Vm-1 where E0 is the amplitude and k is the wave vector. Among the following options, the incorrect choice is

1. The direction of propagation of the electromagnetic wave is along +z
2. The speed of the electromagnetic wave inside the medium is 108 ms-1
3. The wavelength of the electromagnetic wave inside the medium is 300 m
4. The magnetic field is given by the relation By = E0v (kz - 2 106t) where v is the speed of the electromagnetic wave inside the medium

The electric field in a plane electromagnetic wave is given by Ez = 60 (5x + 1.5 109 t) V/m Then expression for the corresponding magnetic field is (here subscripts denote the direction of the field) :

1. Bz = 60 (5x + 1.5 109 t) T
2. By = 60 (5x + 1.5 109 t) T
3. By = 2 10-7 (5x + 1.5 109 t) T
4. Bx = 2 10-7 (5x + 1.5 109 t) T

If the ratio of relative permeability and relative permittivity of a uniform medium is 1 : 4. The ratio of the magnitudes of electric field intensity (E) to the magnetic field intensity (H) of an EM wave propagating in that medium is (Given that 0 0 = 120 ):

1. 30 : 1
2. 1 : 120
3. 60 : 1
4. 120 : 1

In a plane electromagnetic wave travelling in free space, the electric field component oscillates sinusoidally at a frequency of 2.0 1010 Hz and amplitude 48 V m-1. Then the amplitude of oscillating magnetic field is : (Speed of light in free space = 3 108 m s-1)

1. 1.6 10-8 T
2. 1.6 10-7 T
3. 1.6 10-6 T
4. 1.6 10-9 T

The energy that will be ideally radiated by a 100 kW transmitter in 1 hour is

1. 36 107 J
2. 36 104 J
3. 36 105 J
4. 1 105 J

When light propagates through a material medium of relative permittivity r and relative permeability r, the velocity of light, v is given by (c-velocity of light in vacuum)

1. v = c
2. v = r r
3. v = r r
4. v = c r r

The magnetic field of a plane electromagnetic wave is given by B = 3 10-8 (1.6 103 x + 48 1010 t) j, then the associated electric field will be :

1. 9 (1.6 103 x + 48 1010 t) k V/m
2. 3 10-8 (1.6 103 x + 48 1010 t) i V/m
3. 3 10-8 (1.6 103 x + 48 1010 t) i V/m
4. 9 (1.6 103 x - 48 1010 t) k V/m

The ratio of the magnitude of the magnetic field and electric field intensity of a plane electromagnetic wave in free space of permeability 0 and permittivity 0 is (Given that c - velocity of light in free space)

1. 0 0c
2. c
3. 1c
4. c 0 0

For a plane electromagnetic wave propagating in x-direction, which one of the following combination gives the correct possible directions for electric field (E) and magnetic field (B) respectively?

1. - j + k, - j + k
2. j + k, j + k
3. - j + k, - j - k
4. j + k, - j - k

The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is : (c = speed of electromagnetic waves)

1. 1 : 1
2. 1 : c
3. 1 : c2
4. c : 1

Light with an average flux of 20 W/cm2 falls on a non-reflecting surface at normal incidence having surface area 20 cm2. The energy received by the surface during time span of 1 minute is :

1. 12 103 J
2. 24 103 J
3. 48 103 J
4. 10 103 J

An EM wave is propagating in a medium with a velocity v = v i. The instantaneous oscillating electric field of this em wave is along +y axis. Then the direction of oscillating magnetic field of the em wave will be along

1. −z direction
2. +z direction
3. −y direction
4. −x direction

In an electromagnetic wave in free space the root mean square value of the electric field is Erms = 6 V m-1. The peak value of the magnetic field is

1. 2.83 10-8 T
2. 0.70 10-8 T
3. 4.23 10-8 T
4. 1.41 10-8 T

A radiation of energy 'E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (C = Velocity of light)

1. 2EC2
2. EC2
3. EC
4. 2EC

Light with an energy flux of 25 104 W m-2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm2, the average force exerted on the surface is

1. 1.25 10-6 N
2. 2.50 10-6 N
3. 1.20 10-6 N
4. 3.0 10-6 N

An electromagnetic wave of frequency = 3.0 MHz passes from vacuum into a dielectric medium with relative permittivity r = 4.0. Then

1. Wavelength is doubled and frequency becomes half.
2. Wavelength is halved and frequency remains unchanged.
3. Wavelength and frequency both remain unchanged.
4. Wavelength is doubled and frequency unchanged.

The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in vacuum is equal to

1. the speed of light in vacuum
2. reciprocal of speed of light in vacuum
3. the ratio of magnetic permeability to the electric susceptibility of vacuum
4. unity

The electric field of an electromagnetic wave in free space is given by E = 10 (107t + kx ) j V/m, where t and x are in seconds and metres respectively. It can be inferred that Which one of the following pairs of statements is correct ?

1. C and D only
2. A and B only
3. B and C only
4. A and C only

Which of the following statements is false for the properties of electromagnetic waves?

1. Both electric and magnetic field vectors attain the maxima and minima at the same place and same time.
2. The energy in electromagnetic wave is divided equally between electric and magnetic vectors.
3. Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave.
4. These waves do not require any material medium for propagation.

The velocity of electromagnetic radiation in a medium of permittivity 0 and permeability 0 is given by

1. 1 0 0
2. 0 0
3. 0 0
4. 0 0

The velocity of electromagnetic wave is parallel to

1. B E
2. E B
3. E
4. B