Question

Use the following information to answer the next question.

Two plane mirrors, M₁ and M₂ are placed at a right angle. A ray of light is incident on M₁ at P₁and gets reflected from M₁. It then gets reflected from M₂ at P_2.

If OP₁ = OP₂, then the angle of reflection of the ray at P₂ will be

• A. 25°
• B. 45°
• C. 65°
• D. 75°

Answer 1

The correct option is B

45°

The angle of reflection is always equal to the angle of incidence. Let be the angle of incidence at P₁ on mirror M₁. The following figure shows the various angles the light ray makes with the mirrors, M₁ and M₂.

Since ∠M₁OM₂ is 90°, the normal XP₁ on M₁ is parallel to M₂.

Therefore, ∠XP₁P₂ = ∠P₁P₂O =

Since P₁O = OP₂, ∠OP₁P₂ = ∠OP₂P₁ =

∴ 90° − =

2 = 90°

∴ = 45°

Since 90° − = 90° − 45° = 45°, all the angles will be 45°. Hence, all the reflected and the incident angles will be 45°