Previous year MCQs

General science UPPSC 2014 GS-I
Question

To look total image of a person, the minimum height of a plane mirror is:

Answer & Solution

Answer: (Detailed Solution Below)

Option B: Half of the height of a person.

Detailed Solution:

The correct answer is “Half of the height of a person.”.
To see the total image of a person in a plane mirror, the minimum height of the mirror should be Half of the height of the person.

This is because the angle of incidence is equal to the angle of reflection in a plane mirror. So, if you consider the top and bottom points of the person's image, the light rays reflecting from these points to the viewer's eyes will form a triangle with the mirror as its base.

The minimum length of this base (the mirror) is half the height of the person.

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