Question

A ray of light is incident on a glass slab making an angle of ${60}^o$ with the surface. Calculate the angle of refraction in glass if the refractive index of glass is $1.5$

• A. ${19}^o{28}^{\prime }$
• B. ${30}^o$
• C. ${45}^o$
• D. ${50}^o$

Answer 1

The correct option is B ${30}^o$

$\begin{array}{c}\text{at point}A\\ \begin{array}{cc}{\mu }_i\sin i& ={\mu }_r\sin r\\ 1\times \sin {60}^{\circ }& =1.5\times \sin r\\ \sin r& =\frac{\sqrt{3}\times 2}{2\times 3}=\frac{1}{\sqrt{3}}\end{array}\end{array}$

$r={\sin }^{-1}\left(\frac{1}{\sqrt{3}}\right)={\sin }^{-1}\left(0.57\right)$

$r\approx {30}^{\circ }$