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Q55
(NDA-II/2023)
Science & Technology › Basic Science (Physics, Chemistry, Biology)
Official Key
Sita, 1.5 m high, stands before a plane mirror fixed on a wall to view her full image. What should be the minimum height of the plane mirror so that Sita can view her image fully ?
Explanation
According to the principles of optics in physics, to view a full-length image of an object in a plane mirror, the minimum height of the mirror must be exactly half the height of the object.
This is based on the laws of reflection, which state that the angle of incidence is equal to the angle of reflection. When a person views their own image, light rays from the top of the head and from the feet must reflect off the mirror to reach the eyes. Geometrically, this requires a mirror height that is half the person's actual height, regardless of the distance from the mirror.
- Height of Sita (H) = 1.5 m
- Minimum height of mirror required = H / 2
- Calculation: 1.5 / 2 = 0.75 m
Thus, Sita requires a mirror of at least 0.75 m to see her full image, making Option C the correct answer.
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