Which one of the following is the correct angle between the incident and reflected rays when a ray of light incident normally on a plane mirror?

The correct answer is Option 4 (0°). This is based on the fundamental Laws of Reflection and the geometric definition of angles in optics.

According to the Laws of Reflection, the angle of incidence (i) is always equal to the angle of reflection (r). Crucially, these angles are measured with respect to the normal (an imaginary line perpendicular to the mirror's surface).

• When a ray is incident normally, it travels along the normal line itself.
• Therefore, the angle of incidence (i) is 0°.
• By the law i = r, the angle of reflection (r) must also be 0°.
• The ray retraces its path, meaning both the incident and reflected rays lie on the same normal line.

The angle between the incident and reflected rays is the sum of these two angles: 0° + 0° = 0°. Options 1, 2, and 3 are incorrect as they assume the angle is measured from the mirror surface or represent different physical scenarios.