Question

a light ray is allowed to fall on the plane mirror now the mirror is rotated in a plane of incidence then which of the following can not change 1)reflected ray 2)normal 3)incident ray 4) angle of incident

Answer 1

Consider a plane-mirror and a fixed incident ray of light reflecting from the surface at an angle θ Before the mirror has rotated, the angle of incidence is θ as is the angle of reflection.If the mirror is rotated through an angle φ the normal is rotated by an angle φ and thus the angle of incidence increases to θ +φ. Therefore, the angle of reflection must also increase by φ to θ+φ The difference between the final angle of reflection and the initial angle of reflection and is 2φ
For a fixed incident ray, the angle of the reflection is twice the angle through which the mirror has rotated.

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