Question

A ray is reflected in turn by three plain mirrors mutually at right angles to each other. The angle between the incident and the reflected rays is:

• A. ${90}^o$
• B. ${60}^o$
• C. ${180}^o$
• D. None of these

Answer 1

The correct option is C ${180}^o$

The reflected wave will be parallel to the incident wave. This arrangement popularly known as retroflector and widely used in the field of IR spectroscopy
The ray get reflected from the three mirrors and then it will move parallel to the incident ray. It means that it is rotated by an angle of 180.
Option C is the right answer