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 :

Question

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 : (A) 60 cm (B) 24 cm (C) -60 cm (D) -24 cm

Tardigrade Admin · Accepted Answer

When object before a concave mirror line within its focal length, its image is virtual, erect and on the other side. Since he wants his image to lie at

25 c m

from him, it is

15 c m

behind the mirror.

\frac{1}{u} + \frac{1}{v} = \frac{1}{f}

\Rightarrow \frac{1}{- 10} + \frac{1}{15} = \frac{1}{f}

\Rightarrow \frac{- 3 + 2}{30} = \frac{1}{f}

\Rightarrow f = - 30 c m

(Concave mirror)

R = 2 f = - 60 c m

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

$60 c m$

$24 c m$

$- 60 c m$

$- 24 c m$

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

60cm

24cm

−60cm

−24cm

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

$60 c m$

$24 c m$

$- 60 c m$

$- 24 c m$