A beam of light strikes a perfectly smooth plane mirror at an angle of 20° to the normal. What is the angle between the incident ray and the reflected ray?
Answer
40°
The correct answer is 40° — Hence the required angle is 40°.
Step-by-step solution
- Identify the angle of incidence as 20° to the normal.
- Apply the law of reflection: angle of reflection equals angle of incidence, so reflection is 20°.
- Compute the angle between incident and reflected rays: 20° + 20° = 40°.
- Hence the required angle is 40°.
Common mistake: Confusing incident angle with reflected angle
Concept tested: Law of reflection
Published · How this solution was prepared and checked
← All Light questions