Question

ray from sun converge at a point 15 CM in front of a concave mirror where should be an object placed so that its image formed is equal to the size of the object

Answer 1

at 30 cm awoy from the mirror .
here f=15 so at 2f hi=ho .
hence 2f is 30cm.

Answer 2

Answer:  

The same ‘size of the image’ object will be placed at 30 cm.

Explanation:

Given:

The focal length F of concave mirror is 15 cm.

The rays from sun are parallel to main axis after reflection coverage at a point, known as focus. And we know that, same size real and inverted image is formed by concave mirror when object is placed at focus 2F or center of curvature.

So, to form same size image object will be placed at $\bold{15 \times 2=30\ \mathrm{cm}}$.