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You are asked to design a shaving mirror assuming that a person keeps it 10 cm from his face and views the magnified image of the face at the closest comfortable distance of 25 cm. The radius of curvature of the mirror would then be

Asked in JEE Main Online 2015 · Mirror formula and magnification

Answer: (3) 60 cm

Step-by-step solution

The image must be 25 cm from the face, so 15 cm behind the mirror: u=-10 cm, v=+15 cm.

1/f=1/(15)-1/(10)=-1/(30), f=-30 cm.

|R|=2|f|=60 cm

Why the other options are wrong

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