Question

Critical angle of first medium is ${60}^{\circ }$ and it's refractive index 1.732. The refractive index of the second medium is

• A. 1.5
• B. 1.7
• C. 1.6
• D. 2

Answer 1

The correct option is A

1.5

From the definition of Snell law, $sin{\theta }_c$ = $\frac{n_2}{n_1}$.
To get $n_2$, put $n_1$ = 1.732 and ${\theta }_c$ = ${72}^{\circ }$.
Thus we get, sin ${60}^{\circ }$ = $n_2$/1.732 and $n_2$ = 1.5.