Q.

Rays from sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object

1 15 cm in front of the mirror  
2 30 cm in front of the mirror  
3 Between 15 cm and 30 cm in front of the mirror  
4 More than 30 cm in front of the mirror  

Ans.

(2)

In case of a concave mirror, image size becomes equal to the object size when the object distance equals to the radius of curvature i.e., twice the focal length.

So, the object has to be placed at a distance of (15 × 2) = 30 cm in front of a concave mirror.