Question

An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ∈ = 4.0. Then ______.

Options

• wave length is halved and frequency remains unchanged.

• wave length is doubled and frequency becomes half.

• wave length is doubled and the frequency remains unchanged.

• wave length and frequency both remain unchanged.

Answer 1

An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ∈ = 4.0. Then wave length is halved and frequency remains unchanged.

Explanation:

During refraction Velocity of EM wave in hoover, frequency remains unchanged.

`"V"_"vacuum" = 1/(sqrt(mu_0∈_0)) = "c"`

`"v"_"med" = 1/(sqrt(mu_0∈_0xx4)) = "c"/2`

`lambda_"med"/lambda_"vacuum"= "v"_"med"/"v"_"vacuum"`

= `("c"//2)/"c"`

= `1/2`

∴ wave length is halved and frequency remains unchanged.