SSC
PHYSICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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If a man’s face is 25 cm in front of concave shaving mirror producing erect image 1.5 times the size of face, focal length of the mirror would be
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75 cm
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25 cm
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15 cm
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60 cm
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Explanation:
Detailed explanation-1: -Statement II: When a man keeps his face between pole and focus of a mirror an erect and magnified virtual image is formed. A concave mirror forms an erect and there times magnified image on the axis of the mirror at a distance of 32 cm from the object.
Detailed explanation-2: -A person must hold his face at a distance of 20 cm away from the concave mirror so that it may act as a shaving mirror. This is because a concave mirror forms an erect, virtual and magnified image when an object is placed within the focus F, (or, between the focus F and the pole P). Hence, it acts as a shaving mirror.
Detailed explanation-3: -So object should be placed at a distance of 6.667 cm in front of the mirror.
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