During the propagation of electromagnetic waves in a medium:
Electric energy density is equal to the magnetic energy density.
Both electric and magnetic energy densities are zero.
Electric energy density is double of the magnetic energy density.
Electric energy density is double of the magnetic energy density.
C.
Electric energy density is double of the magnetic energy density.
The threshold frequency for a metallic surface corresponds to an energy of 6.2 eV, and the stopping potential for a radiation incident on this surface 5 V. The incident radiation lies in
X-ray region
ultra-violet region
infra-red region
infra-red region
B.
ultra-violet region
An electromagnetic wave in vaccum has the electric and magnetic fields 
and 
which are always perpendicular to each other. the direction of polarisation is given by 
and that of wave propagation by 
then
C.
Assume that a radio station is about 200 km away at your location and the station operates 972 kHz. How long does it take for an electromagnetic signal to travel from the station to you and how many wave crests does it send out per second ?
666 µs and 9.72 × 105 crests per second
666 µs and 972 × 105 crests per second
555 µs and 97.2 × 107 crests per second
555 µs and 0.972 × 105 crests per second
A.
666 µs and 9.72 × 105 crests per second
The speed of radio waves is equal to electromagnetic wave speed i.e. 3 x 108 m/s
Given, the distance of radio station, s = 200 km
= 200 × 103 m
Time taken by radio wave to his toner
The wave emitted send out per second = 972 kHz
= 972 × 103 Hz
= 9.72 × 105 crest per second
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