A ray of light is incident on a plane mirror at an angle 30 with the normal at the point of incidence. The ray will be deviated from its incidence direction by what angle ?

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Q: 83 (CDS-II/2007)
A ray of light is incident on a plane mirror at an angle 30° with the normal at the point of incidence. The ray will be deviated from its incidence direction by what angle ?

question_subject: 

Maths

question_exam: 

CDS-II

stats: 

0,5,12,6,5,6,0

keywords: 

{'incidence direction': [0, 0, 2, 0], 'plane mirror': [0, 0, 0, 7], 'angle': [0, 0, 1, 0], 'ray': [2, 0, 5, 15], 'incidence': [1, 1, 3, 3], 'light': [16, 4, 34, 62]}

When a ray of light is incident on a plane mirror, it follows the law of reflection, which states that the angle of incidence is equal to the angle of reflection. In this case, the ray of light is incident on the mirror at an angle of 30° with the normal (the imaginary line perpendicular to the mirror`s surface) at the point of incidence.

Since the angle of incidence and angle of reflection are equal, the reflected ray will also be at an angle of 30° with the normal. However, since the normal is at a right angle (90°) to the plane mirror`s surface, the reflected ray will be deviated from its incidence direction by twice the angle of incidence. Therefore, the ray of light will be deviated by an angle of 60° from its incidence direction.

Hence, option 2, 60°, is the correct answer.