Question

An electromagnetic wave of frequency $\upsilon =3$ MHz passes from a vacuum into a dielectric medium with permittivity $=4$, Then

• A. Wavelength and frequency both become half.
• B. Wavelength is doubled and frequency remains unchanged.
• C. Wavelength and frequency both remains unchanged.
• D. Wavelength is halfved and frequency remains unchanged.

Answer 1

The correct option is D Wavelength is halfved and frequency remains unchanged.

Frequency remains constant during refraction.

$v_{med}=\frac{1}{\sqrt{{\mu }_0{ϵ}_0\ast 4}}$=$\frac{c}{2}$

$\frac{{\lambda }_{med}}{{\lambda }_{air}}=\frac{v_{med}}{v_{air}}$

= $\frac{\frac{c}{2}}{c}$ =$\frac{1}{2}$

​$\therefore$ wavelength is halved and frequency remains unchanged.