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Difficulty: EasyReflection of Light at Plane and Curved Mirrors

A ray of light strikes a plane mirror at an angle of incidence of 35∘35^\circ. What is the angle of deviation of the reflected ray?

  1. 110∘110^\circAnswer
  2. B
    70∘70^\circ
  3. C
    55∘55^\circ
  4. D
    145∘145^\circ

Answer

The angle of deviation of the reflected ray is 110∘110^\circ.
The angle of deviation dd represents the angle through which a ray of light is turned from its original path. For a plane mirror, d=180∘−2id = 180^\circ - 2i. Substituting i=35∘i = 35^\circ yields d=180∘−70∘=110∘d = 180^\circ - 70^\circ = 110^\circ.

Step-by-Step Solution

1
Identify the given angle of incidence
i=35∘i = 35^\circ
The angle of incidence is measured relative to the normal line.
2
Apply the law of reflection
Angle of reflection r=i=35∘r = i = 35^\circ
The angle of reflection equals the angle of incidence.
3
Calculate the angle of deviation
d=180∘−(i+r)=180∘−2(35∘)=110∘d = 180^\circ - (i + r) = 180^\circ - 2(35^\circ) = 110^\circ
The angle of deviation measures how much the light ray is turned from its original initial straight path.

Key Concept

Angle of deviation for reflection at a plane surface
Estimated Time:45s
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Topics

Reflection of Light at Plane and Curved Mirrors

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