Question

A concave mirror has a focal length of 15 cm. Where should on object be placed in front of this mirror so as to obtain an image which is real, inverted and of the same size as the object?

• A. 20 cm
• B. 30cm
• C. 15 cm
• D. 10cm

Answer 1

The correct option is B 30cm

The real and inverted image created by a concave mirror becomes of equal size to the object when both object and images are situated on the centre of curvature.

This means that the object distance is equal to the radius of curvature for the mirror.

Radius of curvature $=2\times$ focal length of the mirror.

Given, focal length of the mirror $=15cm$

So, object distance $=$ radius of curvature $=2\times 15cm=30cm$