Question

For light incident from air onto a slab of refractive index 2, maximum possible angle of refraction is

• A. ${90}^{\circ }$
• B. ${60}^{\circ }$
• C. ${45}^{\circ }$
• D. ${30}^{\circ }$

Answer 1

Answer: (D)

${30}^{\circ }$

Given,

The refractive index of the glass slab ${\mu }_g=2$

Now applying Snell’s law

${\mu }_a\sin i={\mu }_g\sin r$

Where $i$ is the angle of incidence and $r$ is the angle of refraction

$\frac{\sin i}{\sin r}=\frac{{\mu }_g}{{\mu }_a}$

Maximum angle of incidence is $i={90}^{\circ }$, ${\mu }_g=2$ and, ${\mu }_a=1$(refractive index of air)

$\frac{\sin {90}^{\circ }}{\sin r}=\frac{2}{1}$

$\sin r=\frac{1}{2}$

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

The maximum possible angle of refraction is ${30}^{\circ }$ .