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Which of the following have zero average value in a plane electromagnetic wave?

1) Electric energy 2) Magnetic energy 3) Electric field 4) Both magnetic and electric field Answer: 4) Both magnetic and electric field... View Article

According to Maxwell, a changing electric field produces

1) Emf 2) Electric current 3) Magnetic field 4) Radiation pressure Answer: 3) Magnetic field Solution: From Maxwell's law ... View Article

Which of the following radiations has the least wavelength?

1) γ-rays 2) β-rays 3) α-rays 4) X-rays Answer: 1) γ-rays Solution: γ-rays have the maximum energy out of... View Article

The SI unit of displacement current is ________

1) Coulomb 2) Henry 3) Ampere 4) Faraday Answer: 3) Ampere Solution: The SI unit of displacement current is Ampere... View Article

If the wavelength of light is 4000^o A then the number of waves in 1mm length will be _________

1) 2.5 2) 2500 3) 250 4) 25000 Answer: 2) 2500 Solution: λ = 4000o A = 4000 x 10-10 m If there are n number of... View Article

The velocity of light in vacuum can be changed by changing _____________

1) Frequency 2) Wavelength 3) Amplitude 4) None of these Answer: 4) None of these Solution: The speed of light remains constant in... View Article

In T.V. broadcasting both pictures and sound are transmitted simultaneously.

In this 1) audio signal is frequency modulated and video signal is amplitude modulated 2) both audio and video signals are frequency modulated... View Article

Television signals reach us only through the ground waves. The range R related with the transmitter height h is in proportion to

1) h 2) h1/2 3) h-1/2 4) h-1 Answer: 2) h1/2 Solution: Range, R = √2hr where r is the radius of the earth... View Article

Consider the following statements about electromagnetic radiations; All of them

(i) have energy (ii) exert pressure on an object (iii) have the same momentum Of these statements 1) (i), (ii) and (iii) are correct 2) (i)... View Article

In fog, photographs of the objects taken with infrared radiations are more clear than those obtained during visible light because

1) IR radiation has a lesser wavelength than visible radiation 2) scattering of IR light is more than visible light 3) the intensity of IR... View Article

A parallel plate capacitor is charged to 60 µC. Due to a radioactive source, the plate loses charge at the rate of 1.8 × 10 ^-8 Cs^-1. The magnitude of displacement current is

1) 1.8 × 10-8 Cs-1 2) 3.6 × 10-8 Cs-1 3) 4.1 × 10-11 Cs-1 4) 5.7 × 10-12 Cs-1 Answer: 1) 1.8 ×... View Article

A perfectly reflecting mirror has an area of 1 cm². Light energy is allowed to fall on it for 1 h at the rate of 10 Wcm^-2. The force that acts on the mirror is

1) 3.35 × 10-8 N 2) 6.7 × 10-8 N 3) 1.34 × 10-7 N 4) 2.4 × 10-4 N Answer: 2) 6.7 × 10-8 N Solution:... View Article

The rms value of the electric field of the light coming from the sun is 720 NC ^-1. The average total energy density of the electromagnetic wave is

1) 4.58 × 10-6 Jm-3 2) 6.37 × 10-9 Jm-3 3) 81.35 × 10-12 Jm-3 4) 3.3 × 10-3 Jm-3 Answer: 1) 4.58 ×... View Article

Radiation of energy E falls normally on a perfectly reflecting surface. The momentum transferred to the surface is

1) E/c 2) 2E/c 3) Ec 4) E/c2 Answer: 2) 2E/c Solution: The momentum of the photon = E/c Change in momentum = E/c - (-E/c) = 2E/c =... View Article

Radiations of intensity 0.5 Wm ^-2 are striking a metal plate. The pressure on the plate is

1) 0.166 × 10-8 Nm-2 2) 0.332 × 10-8 Nm-2 3) 0.111 × 10-8 Nm-2 4) 0.083 × 10-8 Nm-2 Answer: 1) 0.166 ×... View Article

A plane EM wave travels in free space along X-axis. At a particular point in space, the electric field along Y-axis is 9.3 Vm ^-1. The magnetic induction is

1) 3.1 × 10-8 T 2) 3 × 10-5 T 3) 3 × 10-6 T 4) 9.3 × 10-6 T 5) 3.1 × 10-7 T Answer: 1) 3.1 ×... View Article

The sun delivers 10³ Wm^-2 of electromagnetic flux on the earth’s surface. The total power that is incident on a roof of dimensions 6 m × 30 m, is

1) 1.8 × 105 W 2) 7.2 × 105 W 3) 0.9 × 105 W 4) 4.5 × 105 W Answer: 1) 1.8 × 105 W Solution:... View Article

The refractive index and the permeability of a medium are 1.5 Hm^{– 1} and 5 × 10^-7 Hm ^-1 respectively. The relative permittivity of the medium is nearly

1) 25 2) 15 3) 81 4) 10 5) 6 Answer: 5) 6 Solution: The refractive index of the medium is given by n = c/v v = c/n = 3 x... View Article

If 150 J of energy is incident on area 2 m². If Qr =15 J, coefficient of absorption is 0.6, then the amount of energy transmitted is

1) 50 J 2) 45 J 3) 40 J 4) 30 J Answer: 2) 45 J Solution: When the thermal radiation falls on a body, it will be partly reflected,... View Article

If a source is transmitting electromagnetic waves of frequency 8.196 × 10⁶ Hz, then the wavelength of the electromagnetic waves transmitted from the source will be

1) 5090 cm 2) 4050 cm 3) 4230 cm 4) 3660 cm Answer: 4) 3660 cm Solution: Given, Frequency of the electromagnetic waves, f... View Article

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