Question

The refractive index of glass is $1.5$. From a point $P$ inside a glass block, draw rays $PA,PB$ and $PC$ incident on the glass-air surface at an angle of incidence ${30}^o,{42}^o$ and ${60}^o$ respectively. What is the angle of refraction for the ray $PB$ ? (Take $\sin {42}^o=\frac{2}{3}$ )

• A. $0^o$
• B. ${30}^o$
• C. ${60}^o$
• D. ${90}^o$

Answer 1

The correct option is D ${90}^o$

According to Snell's Law: $\frac{sini}{sinr}=\frac{n_2}{n_1}$
Substituting, $\frac{sin{42}^o}{sinr}=\frac{1}{1.5}$
Thus, $sinr=\frac{1.5}{1.5}=1$
Thus, $r={90}^o$