Question

The incident ray and the reflected ray from a mirror is mutually perpendicular to each other. Find the angle of incidence.

• A. $0^{\circ }$
• B. ${90}^{\circ }$
• C. ${30}^{\circ }$
• D. ${45}^{\circ }$

Answer 1

Answer: (D)

${45}^{\circ }$

The angle of incidence is the angle between this normal line and the incident ray; the angle of reflection is the angle between this normal line and the reflected ray. According to the law of reflection, the angle of incidence equals the angle of reflection.

So, $i=r$

Given, $i+r={90}^0$

$⟹$ $i+i={90}^0$

or, $2i={90}^0$

or, $i={45}^0$