Question

Two plane mirrors are inclined to each other at ${70}^{\circ }$ facing to each other. A ray incident on one mirror at an angle $\theta$. The ray reflected from this mirror falls on second mirror from where it is reflected parallel to the first mirror. Determine the value of $\theta$.

Answer 1

Step 1:

Drawing two mirrors at an angle of ${70}^{\circ }$and the final reflected ray parallel to the first mirror.

Step 2:

Retracing the incident ray backwards using the second law of reflection that is the angle of incidence should be equal to the angle of reflection = ${20}^{\circ }$

Step 3:

Following the same step as step 2 and finding the value of $\theta$.

Hence, the value of $\theta$ is ${50}^{\circ }$.