Question

To travel through the same distance in two different media, a light ray of certain frequency takes different times which are in the ratio 3: 5, the relative refractive index is :

• A. 5/3
• B. 3/2
• C. 5/2
• D. 7/5

Answer 1

The correct option is A 5/3

Speed of light in medium is
$v=\frac{c}{\mu }$
So, $t=\frac{D}{V}=\frac{D\mu }{C}$ [Let D is the distance travelled]
So, $\frac{t_1}{t_2}=\frac{D{\mu }_1}{C}\times \frac{C}{D{\mu }_2}$
$\Rightarrow \frac{{\mu }_1}{{\mu }_2}=\frac{t_1}{t_2}$
= $\frac{3}{5}$ or ${\mu }_2=\frac{5}{3}{\mu }_1$
So, relative refractive index is $\frac{5}{3}$