## Question

A pin is placed 10 cm in front of a convex lens of focal length 20 cm and refractive index 1.5. The surface of the lens farther away from the pin is silvered and has a radius of curvature of 22 cm. How far from the lens is the final image formed?

### Solution

11 cm

The value of the effective focal length *F* is given by

Since the convex lens with a silvered surface behaves as a concave mirror of effective focal length *F*, we have

Substituting these values in the mirror formula

The negative sign shows that the image is in front of the effective mirror and hence is real.

#### SIMILAR QUESTIONS

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