Question

A light ray incident at a point $O$ on a plane mirror $MM$ and reflected back as shown in figure, then choose the correct option.

• A. The angles $\alpha ,d$ always remain same
• B. The angle of deviation $d=\pi -2i=2\alpha$
• C. The angles $\alpha ,i$ are always supplementary
• D. both $1$ and $3$

Answer 1

The correct option is B The angle of deviation $d=\pi -2i=2\alpha$

- Angle $\alpha$ \& $d$ are dependent upon angle of incidence

option $A^{\prime }$ is wrong as they are

option Same.

$\text{as}d+L+L\gamma =\pi$

(Li= Lr rule of reflection)

$\therefore$

$[2\alpha =\pi -2i]$

$[ie=L]$

$\therefore Ld=\pi -2Li$

So, option 'B' is correct.

Normal always make ${90}^{\circ }$ with Mirror

$\therefore L\alpha +Li={90}^{\circ }$ (i.e complemantry

not suplementry)

only option $B$ ' is correct