Electromagnetic Waves · Question 13

The ratio of speeds of electromagnetic waves in vacuum and a medium, having dielectric constant k = 3 and permeability of = 2 0, is ( 0 = permeability of vacuum)

1. 6 : 1
2. 3 : 2
3. 6 : 1
4. 36 : 1

The electric field of a plane electromagnetic wave, travelling in an unknown nonmagnetic medium is given by, Ey = 20 (3 106 x - 4.5 1014 t ) V/m (where x, t and other values have S.I. units). The dielectric constant of the medium is (speed of light in free space is 3 108 m/s)

A laser beam has intensity of 4.0 1014 W/m2. The amplitude of magnetic field associated with beam is T. (Take 0 = 8.85 10-12 C2/Nm2 and c = 3 108 m/s)

1. 1.83
2. 2.0
3. 5.5
4. 18.3

If , E and t represent the free space permittivity, electric field and time respectively, then the unit of Et will be :

1. Am
2. A/m
3. A/m2
4. Am2

The electric field in a plane electromagnetic wave is given by : Ey = 69 [0.6 103x - 1.8 1011t ] V/m. The expression for magnetic field associated with this electromagnetic wave is T.

1. Bz = 2.3 10-7 [0.6 103x - 1.8 1011t ]
2. Bz = 2.3 10-7 [0.6 103x + 1.8 1011t ]
3. By = 2.3 10-7 [0.6 103x - 1.8 1011t ]
4. By = 69 [0.6 103x + 1.8 1011t ]

An electromagnetic wave of frequency 100 MHz propagates through a medium of conductivity, = 10 mho/m. The ratio of maximum conduction current density to maximum displacement current density is . [Take 14 0 = 9 109 N m2/C2]

If 0 denotes the permittivity of free space and E is the flux of the electric field through the area bounded by the closed surface, then dimensions of ( 0 d Edt ) are that of :

1. electric charge
2. electric field
3. electric current
4. electric potential

The unit of 2I 0 c is : (I = intensity of an electromagnetic wave, c = speed of light)

1. Vm
2. NC-1
3. NC
4. Nm

If an optical medium possesses a relative permeability of 10 and relative permittivity of 10.0885, then the velocity of light is greater in vacuum than that in this medium by times. ( 0 = 4 10-7 H/m, 0 = 8.85 10-12 F/m, c = 3 108 m/s)

The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed 2 m away from it, is

1. 3 10-8 Pascals
2. 0
3. 1.5 10-8 Pascals
4. 6 10-8 Pascals