Question

A ray of light is incident on a glass plate. The light ray travels distance of 5 cm inside the glass plate before emerging out of the glass plate. If the incident ray suffers a deviation of ${30}^0$. the perpendicular distance between incident and the emergent ray is

• A. 5 cm
• B. 2.5 cm
• C. 7.5 cm
• D. 10 cm

Answer 1

The correct option is B 2.5 cm

$t\to$ thickness of glass plate

$d\to$ lateral displacement

$d=\left(\frac{t}{\cos r}\right)\sin \left(i-r\right)$

$d=\frac{5\cos \left(\theta -30\right)}{\cos \left(\theta -30\right)}\sin \left[\theta -\left(\theta -30\right)\right]$

$=5\sin 30$

$=\frac{5}{2}$ $=2.5$

Hence,

option $\left(B\right)$ is correct answer.