Question

A plane mirrior is inclined to horizontal at 60. A ray of light is incident on the mirror at an angle of incidence 30 as shown. Angel which the reflected ray makes with horizontal is

• A. $30$
• B. $60$
• C. $0$
• D. $45$

Answer 1

The correct option is C $0$

$\text{angle of incidence = angle of reflection}$

$\angle AOC=\angle BOC$

$\angle BOC={30}^{\circ }$

Now, $\angle POC=90$ (normal line)

$\therefore △BOC+\angle BOP=90$

$\Rightarrow {30}^{\circ }+\angle BOP={90}^{\circ }$

$\therefore \angle BOP={60}^{\circ }$

but $\angle OPB={60}^{\circ }$

So $\angle OPB=\angle BOP={60}^{\circ }$

these are alternate angle pair of line

$OB$ and $PQ$

Hence, $OB//PB$.

SO, reflected ray makes $0^{\circ }$ with horizontal

Hence, $\left(C\right)$ is correct option.