Question

A beam of light striking the surface of a glass plate from the air as shown in above figure.
Let $n$ denote the index of refraction of the glass. If the incident light has a frequency of $f$ when travelling through the air, Find out the wavelength of the light when it travels through the glass?

• A. $fc/n$
• B. $n/fc$
• C. $c/f$
• D. $nc/f$
• E. $c/nf$

Answer 1

The correct option is E $c/nf$

Let the velocity and wavelength of light in glass be $v$ and $\lambda$ respectively.

Speed of light in air $v_a=c$ m/s

Using $n_a{v}_a=n_g{v}_g$

$\therefore$ $1\times c=n\times v$

OR $c=n\times \left(\lambda f\right)$ $⟹\lambda =\frac{c}{nf}$