Question

An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with relative permittivity ∈ = 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 1

Correct option  (b) Wavelength is halved and frequency remains unchanged.

Explanation:

Frequency of electromagnetic wave does not change with change in medium but wavelength and velocity of wave changes with change in medium. 

Velocity of electromagnetic wave in vacuum

Velocity of electromagnetic wave in the medium

where μ_r  and ∈_r be relative permeability and relative permittivity of the medium. 

For dielectric medium, μ_r =1

Wavelength of the wave in medium