A man is 180 cm tall and his eyes are 10 cm below the top of his head. In order to see his entire height right from toe to head, he uses a plane mirror kept at a distance of 1 m from him. The minimum length of the plane mirror required isSelect an answerA180 cmB90 cmC85 cmD170 cm
Question
A man is 180 cm tall and his eyes are 10 cm below the top of his head. In order to see his entire height right from toe to head, he uses a plane mirror kept at a distance of 1 m from him. The minimum length of the plane mirror required isSelect an answerA180 cmB90 cmC85 cmD170 cm
Solution
The minimum length of the mirror required to see the full height of a person is half the person's height. This is because the angle of incidence equals the angle of reflection, so the light from the top of the person's head and the light from their feet will both hit the mirror and reflect back at the same angle, allowing the person to see their full height.
In this case, the man's height is 180 cm. Therefore, the minimum length of the mirror required is 180 cm / 2 = 90 cm.
So, the correct answer is B90 cm.
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