Question

A ray PQ incident normally on the refracting face BA is refracted in the prism BAC made of material of refractive index 1.5. Complete the path of ray through the prism. From which face will the ray emerge? Justify your answer.

Answer 1

We know from Snell's Law,

$n=\frac{1}{sinC}$

Where, $n=$ Refractive index

$C=$ Critical angle.
According to the question refractive index of the material of the prism is 1.5
So, $sinC=\frac{1}{n}=\frac{1}{1.5}=0.667$

Or,
$sinC=sin{41}^{\circ }{49}^{\prime }$

Or,
$C={41}^{\circ }{49}^{\prime }$

Incidence angle in this case is ${30}^0$

It means that

$C>{30}^{\circ }$

If critical angle is greater than incidence angle then ray will emerge out

Thus, the light ray PQ will emerge out from the side AC