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Question
Use the following information to answer the next question.
A ray is reflected from a plane surface. It makes an angle of 20° with the reflecting surface.
What is the angle of incidence?
Use the following information to answer the next question.
A ray is reflected from a plane surface. It makes an angle of 20° with the reflecting surface.
What is the angle of incidence?
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Solution
The correct option is B 70°
The angle of reflection is always equal to the angle of incidence. The given ray is reflected at an angle of 20° with the reflecting surface. The stated situation is shown in the following ray diagram, where is the angle of incidence and is the angle of reflection.
According to the law of reflection:
=
Let the incident ray make an angle with the reflecting surface.
The sum of the angles , , , and 20° will be 180°.
∴ + ++ 20° = 180°
Since = , = 20°
2 = 180° − 40° = 140°
∴ = 70°
Hence, the angle of incidence is 70°.
70°
The angle of reflection is always equal to the angle of incidence. The given ray is reflected at an angle of 20° with the reflecting surface. The stated situation is shown in the following ray diagram, where is the angle of incidence and is the angle of reflection.
According to the law of reflection:
=
Let the incident ray make an angle with the reflecting surface.
The sum of the angles , , , and 20° will be 180°.
∴ + ++ 20° = 180°
Since = , = 20°
2 = 180° − 40° = 140°
∴ = 70°
Hence, the angle of incidence is 70°.
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