A ray is incident on a plane mirror. Its reflected ray makes an angle of 80 degree
to the incident ray. Find the
angle of incidence.

Solution,
From the laws of reflection, angle of incidence is equal to the angle of reflection.
Given, the reflected ray makes an angle 80^o with the incident ray.
Angle between incident ray and reflected ray 
 $$\begin{gathered} =2\times angle of incidence={80}^o \\ Thus, \\ angle of incidence = \frac{{80}^o}{2}={40}^o \end{gathered}$$
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