Question 15 of 295

Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror $\left({M}_{1}\right)$ and parallel to the second mirror $({M}_{2})$ is finally reflected from the second mirror $({M}_{2})$ and parallel to the first mirror $\left({M}_{1}\right).$ The angle between the two mirrors will be:

A${60}^{o}$B${45}^{o}$C${90}^{o}$D${75}^{o}$

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Answer: (A) ${60}^{o}$

As given in question $AB||CO$

$∴\angle ABF=\theta$

From laws of reflection

$\angle OBC=\theta$

Similarly $CD‖OB$

$∴\angle DCE=\theta$

Again from laws of reflection,

$\angle OCB=\theta$

$∴3\theta ={180}^{o}$

$\Rightarrow \theta ={60}^{o}$