An electromagnetic wave of frequency 2 MHz propagates from vacuum to a non - magnetic medium of relative permittivity 9. Then its ' wavelength

Options

A. increases by 100 m
B. increases by 50 m
C. decreases by 50 mm
D. decreases by 100 m

Answer

D

Explanation

In vacuum wavelength, `lambda_(0) = ( c)/(f_0)= (3 xx 10^8)/(2 xx 10^6)= 1.5 xx 10^2 = 150 m`
In medium, speed of wave is
`v= (c )/(sqrt(epsilon_r mu_r ))~~ (c )/(sqrt(epsilon _r))`
(as medium, speed of wave is)
`therefore v= ( c)/(sqrt(9))=c/3= 1 xx 10^8 ms^(-1)`
Frequency remaining same, wavelength in medium `lambda = (v)/(f_0) = (10^8)/(2 xx 10^6) = 50`m
`therefore` Wavelength decreases by 100 m .