CBSE Class 12 Physics Electromagnetic Waves Assignment Set B

Important Questions for NCERT Class 12 Physics Electromagnetic Waves

Question. 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

(a) –z direction
(b) +z direction
(c) –y direction
(d) –x direction

Answer B


Question. 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
(a) 2.83 × 10^–8 T
(b) 0.70 × 10^–8 T
(c) 4.23 × 10^–8 T
(d) 1.41 × 10^–8 T

Answer A
 

Question. Which of the following are not electromagnetic waves? 
(a) cosmic rays
(b) g-rays
(c) b-rays
(d) X-rays

Answer C


Question. Out of the following options which one can be used to produce a propagating electromagnetic wave ?
(a) A chargeless particle
(b) An accelerating charge
(c) A charge moving at constant velocity
(d) A stationary charge 

Answer B

Question. 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
(a) 1.25 × 10^–6 N
(b) 2.50 × 10^–6 N
(c) 1.20 × 10^–6 N
(d) 3.0 × 10^–6 N 

Answer B


Question. An electromagnetic wave of frequency u = 3.0 MHz passes from vacuum into a dielectric medium with relative permittivity e = 4.0. Then
(a) Wavelength is doubled and frequency becomes half.
(b) Wavelength is halved and frequency remains unchanged.
(c) Wavelength and frequency both remain unchanged.
(d) Wavelength is doubled and frequency unchanged

Answer B
 

Question. The electric field associated with an em wave in vacuum is given by [E = i ^ 40 cos (kz – 6 × 108t)]; where E, z and t are in volt/m, meter and seconds respectively. The value of wave vector k is
(a) 2 m^–1
(b) 0.5 m^–1
(c) 6 m^–1
(d) 3 m^–1 

Answer A
 

Question. Which of the following electromagnetic radiations have the smaller wavelength?   
(a) X-rays
(b) g-rays
(c) UV waves
(d) microwaves 

Answer  B
 

Question. According to Maxwell’s hypothesis, changing of electric field give rise to :    
(a) magnetic field
(b) pressure gradient
(c) charge
(d) voltage

Answer  A


Question. Frequency of infrared wave is approximately:   
(a) 1018 Hz
(b) 1014 Hz 
(c) 109 Hz
(d) 1016 Hz

Answer  B

Please refer to attached file for CBSE Class 12 Physics Electromagnetic Waves Assignment Set B