Question

A ray of light is ancident at angle of ${35}^{\circ }$ on a plane mirror. What is angle $\theta$?

• A. ${35}^{\circ }$
• B. ${45}^{\circ }$
• C. ${55}^{\circ }$
• D. none of these

Answer 1

The correct option is A ${35}^{\circ }$


From the figure N is the normal
hence $i-{35}^0={90}^0$
$i={90}^0-{35}^0={55}^0$
Now from the laws of reflection
$i=r$
Hence $r={55}^0$
and from the figure
$r+\theta ={90}^0$
$\theta ={90}^0-r={90}^0-{55}^0$
$\theta ={35}^0$