Archives

The electric field of a plane electromagnetic wave varies with time of amplitude 2 Vm^-1 propagating along the Z-axis. The average energy density of the magnetic field is (in Jm^-3)

1) 13.29 × 10-12 2) 8.85 × 10-12 3) 17.72 × 10-12 4) 4.43 × 10-12 5) 2.22 × 10-12 Answer: 2) 8.85 ×... View Article

When an electromagnetic wave encounters a dielectric medium, the transmitted wave has

1) same frequency but different amplitude 2) same amplitude but different frequency 3) same frequency and amplitude 4) different frequency and... View Article

When a plane electromagnetic wave travels in a vacuum, the average electric energy density is given by (E_o is the amplitude of the electric field)

1) (1/4)ε0E02 2) (1/2)ε0E02 3) 2ε0E02 4) 4ε0E02 Answer:1) (1/4)ε0E02 Solution: u =... View Article

At room temperature, if the relative permittivity of water is 80 and the relative permeability be 0.0222 then the velocity of light in water is __________ m/s

1) 2.5 x 108 2) 2.25 x 108 3) 3.5 x 108 4) 3 x 108 Answer: 2) 2.25 x 108 Solution: V = 1/√μ0ε0 V'... View Article

Maxwell’s equations are derived from the laws of ___________

1) electricity 2) magnetism 3) both electricity and magnetism 4) mechanics Answer: 3) both electricity and magnetism Solution:... View Article

Electromagnetic waves are produced by

1) a static charge 2) a moving charge 3) an accelerating charge 4) chargeless particles Answer: 3) an accelerating charge Solution: An... View Article

The amplitude of the electric field in a parallel beam of light of intensity 4.0 Wm^–2 is __________

1) 54.87 NC–1 2) 19.4NC–1 3) 9.7NC–1 4) None of these Answer: 1) 54.87 NC–1 Solution: The intensity... View Article

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

M	T	W	T	F	S	S
				1	2	3
4	5	6	7	8	9	10
11	12	13	14	15	16	17
18	19	20	21	22	23	24
25	26	27	28	29	30	31