Question

A ray of light on striking a polished surface changed its direction by 90 degrees. Find the angles of incidence and reflection wrt the normal.

Answer 1

We know that angle of incidence is equal to the angle of reflection, i.e., $\angle$i = $\angle r$. .......(1)
Now, the angle between the incident and the reflected ray is$\angle$ i + $\angle$r.
Given, the angle between the incident and the reflected ray is 90⁰.
So,, we get
$\angle$i +$\angle$ r = 90⁰
From equation (1), we get :-
$\angle$i + $\angle$ i = 90⁰
or
Therefore $\angle i=\angle r$ = 45⁰ with the normal.