Question

Total internal reflection in a non-magnetic medium occurs at $\theta \ge {45}^o$. In terms of velocity of light in vacuum (c), the velocity of light in this medium is

• A. $c$
• B. $0.707c$
• C. $\sqrt{\frac{3}{2}}c$
• D. $\frac{2}{3}c$

Answer 1

The correct option is B $0.707c$

$\mu =\frac{1}{sinC}=\frac{1}{sin45}=\frac{1}{sin{45}^o}=\sqrt{2}$

Now $V_m=\frac{v_a}{\mu }=\frac{c}{\sqrt{2}}=0.707c$