Question

Question 10
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?

(a) 15 cm in front of the mirror
(b) 30 cm in front of the mirror
(c) between 15 cm and 30 cm in front of the mirror
(d) more than 30 cm in front of the mirror

Answer 1

(b) 30 cm in front of the mirror

The object kept at the centre of curvature of a concave mirror will produce an image with same size as that of the object.
We know that 2f = C
Here, f = 15 cm
$\Rightarrow$ C = 2 x 15 = 30 cm
$\therefore$ Object should be placed at 30 cm from the concave mirror.