Question

An incident ray strikes a plane mirror at an angle of ${20}^o$ with respect to horizontal surface as shown. What is the change in the angle of reflection, if the incident ray moves towards normal by $1^o$?

Answer 1

Now angle of distance $i={90}^0-{20}^0={70}^0$

Angle of reflection is $r=i={70}^0$ (from laws of reflection)

If angle of incidence decreases by $1^0$ so angle of reflection will also decrease by $1^0$.