An electromagnetic wave of frequency ν = 3.0 MHz passes

An electromagnetic wave of frequency ν = 3.0 MHz passes from vacuum into a dielectric medium with relative permittivity ε = 4.0. Then

1. wavelength is doubled and frequency is unchanged
2. wavelength is doubled and frequency becomes half
3. wavelength is halved and frequency remains unchanged
4. wavelength and frequency both remain unchanged

Given: frequency f = 2MHz, relative permittivity ∈_r = 4
From formula,

velocity v =	c
	√∈_r

=	c
	2

⇒ λ' =	λ
	2

[Since frequency remains unchanged]