Question

A glass prism has refractive index 1.5 and the refracting angle is ${90}^o$. If a ray falls on it at an angle of incidence of ${30}^o$, then angle of emergence will be

• A. ${60}^o$
• B. ${30}^o$
• C. ${45}^o$
• D. The ray will not emerge out of his prism

Answer 1

Answer: (D)

The ray will not emerge out of his prism

We have, $\delta =(\mu -1)A$

$=(1.5-1)\times 90$

$=0.5\times 90$

$={45}^o$

Now, $\delta =(i_1+i_2)-A$

$\therefore i_2=\delta -i_1+A$

$=45-30+{90}^o$

$={105}^o$

Angle of emergence has inclination with second surface

$=90-105$

$=-15$

This shows that light ray will not emerge out of the prism.