Question

Two plane mirrors AB and AC are inclined at an angle = 20°. A ray oflight starting from point P is incident at point Q on the mirror AB, thenat R on mirror AC and again on S on AB finally the ray ST goes parallelto mirror AC. The angle which the ray makes with the normal at point QA) 20°C) 40°D) 60°B) 30°​

Answer 1

Answer:

A ray oflight starting from point P is incident at point Q on the mirror AB, thenat R on mirror AC and again on S lly the ray ST goes...

Answer 2

The angle which the ray makes with the normal at point Q is 20° .

• For the last reflected light ray to be parallel to the AC , the light ray from Q should hit AC perpendicular to it.
• The reflected light ray will follow the incident ray.
• If we consider the triangle made by the two triangles and the light ray, we can see that the angle made by the ray with the mirror is 70°
• The angle made with the normal is 90° - 70° = 20°
• Therefore the angle which the ray makes with the normal at point Q is 20°.