## Question

A concave mirror forms a real image four times the size of the object placed at a distance of 10 cm from it. What is the radius of curvature of the mirror?

### Solution

16 cm

Since the image is erect, the magnification is negative. Hence

*m* = – 4.

Also *u* = – 10 cm

Substituting for *u* and *v* in the formula

We have *f* = –8 cm.

Hence *R* = 2*f* = –16 cm.

The negative sign is expected since the mirror is concave.

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