MCQ Physics - Topic Electromagnetic Wave
Que 1
The dimensional formula of
1/(magnetic permeability×electric permittivity)
a) [LT^-1]
b) [L^-1T]
c) [L^2T^-2]
d) [TL]
Ans (c)
Que 2
The electromagnetic wave which has least wavelength
a) Radio waves
b) X rays
c) microwaves
d) Gamma waves
Ans (d)
Que 3
The electromagnetic wave which has longest wavelength
a) Radio waves
b) X rays
c) microwaves
d) Gamma waves
Ans (a)
Que 4
Electric and magnetic field in an electromagnetic wave are
a) mutually perpendicular and in same phase
b) mutually perpendicular and in opposite phase
c) parallel to each other and same phase
d) parallel to each other and in opposite phase
Ans (a )
Que 5
Find the energy of photon of electromagnetic radiation of wavelength 200 A°
a) 1.76×10^-18 J
b) 0.99×10^-18 J
c) 1.76
d) 0.99
Ans (b)
Hint
Formula used
E=hc/wavelength(lambda)
Que 6
Find the speed of light in air if an electromagnetic wave is travelling in air whose dielectric constant is k = 1.006
a) 3×10^8 m/s
b) 3.88 ×10^8 m/s
c) 2.5×10^8 m/s
d) 4.6×10^8 m/s
Ans (a)
Hint
Formula used
v=c/√k
Que 7
Calculate the wavelength of a radio wave of frequency 1 MHz
a) 400m
b) 300 m
c) 350 m
d) 200 m
Ans (b)
Formula used
Velocity =frequency×wavelength
Que 8
An electromagnetic wave with pointing vector 5W/m^2 is absorbed by the surface of some area if the force on the surface is 10^-7 N find the area
a) 6 m^2
b) 3 m^2
c) 60m^2
d) 4 m^2
Ans (a)
Hint
P=I/c= 5/(3×10^8)
F = P×A
Que 9
The rays produced in sonography are
a) microwave
b) infrared
c) sound waves
d) ultrasound
Ans (d )
Que 10
Find the average power per unit area at a distance of 2 m from a small bulb if the bulb emits 20 watt of electromagnetic radiation uniformly in all directions
a) 0.69 W/m^2
b) 0.56 W/m^2
c) 0.78 W/m^2
d) 0.39 W/m^2
Ans (d )
Hint
I=P/(4πr^2)
Fri Nov 18, 2022