What is the point at which the incident ray falls on the mirror called? If a ray of light is incident on a plane mirror at an angle of 30 degrees, what is its angle of reflection?

Expert Answers
gsenviro eNotes educator| Certified Educator

Let's review reflection of light rays from a plane mirror. 

When a ray of light is incident on a plane mirror, it is known as an incident ray and it falls on the mirror at a point known as the point of incidence. If a normal to the mirror is drawn at the point of incidence, we find that the angle made by the incident ray with this normal (also known as angle of incidence) is equal to angle made by the reflected ray with this normal. Thus, if a light ray is incident at an angle of 30 degrees to the mirror, its angle of incidence is 60 degrees (= 90 - 30 degrees) and hence its angle of reflection would also be 60 degrees. If a light ray is normal to the mirror, the angle of incidence and angle of reflection will both be 0 degrees and the ray will retrace its path. The images made by a plane mirror are virtual images and the distance of an object in front of the mirror is equal to the distance of the image behind the mirror.

Hope this helps. 

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