Question

There are two plane mirrors placed at some angle $\theta$ with each other. A ray incident on first mirror (travelling parallel to second mirror) , travels parallel to the first mirror after two successive reflections. Find the angle $\theta$ between the mirrors.

• A. ${90}^o$
• B. ${60}^o$
• C. ${120}^o$
• D. ${30}^o$

Answer 1

The correct option is B ${60}^o$

By geometry, we can write as :
$360-2\theta =180+\theta$

$3\theta =180$

$\theta ={60}^o$