Question

Find the refractive index of the core of an optical fiber if the critical angle is ${60}^{\circ }$ and the refractive index of the cladding is $\sqrt{3}$?

• A. $\sqrt{2}$
• B. $2$
• C. $3$
• D. $2.5$

Answer 1

The correct option is B

$2$

We know that optical fibre works on the principle of Total Internal Reflection.

Applying Snell's law
$sin{\theta }_C=\frac{\text{R.I of Rarer Medium}}{\text{R.I of Denser medium}}\Rightarrow sin{60}^{\circ }=\frac{\text{R.I of cladding}}{R.Iofcore}\Rightarrow \frac{\sqrt{3}}{2}=\frac{\sqrt{3}}{n}\Rightarrow n=2$
Hence, the correct option is 'B'.