JEE Main 2015 · 10 Apr · Shift 1 · Physics Q24

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PhysicsSingle correct+4 / -1Question 24 of 90

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 :

30 cm

24 cm

60 cm

−24 cm

Answer and worked solution

Official answer: C

The image is virtual and erect, 25 cm from the face, i.e. 15 cm behind the mirror: $u=-10$ and $v=+15$ cm.
$\frac1f=\frac1{15}-\frac1{10}\implies f=-30\text{ cm},$
a concave mirror with $|R|=60$ cm.

Topics:Spherical mirrors

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JEE Main 2015 · 10 Apr · Shift 1, Physics question 24