Question

Rays from the 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? [NCERT Exemplar]
(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

ANSWER :-

30 cm from the mirror

EXPLAINATION :-

In a concave mirror the converging point is its focal length

Therefore, F = - 15 cm

So, Center of the curvature = -30 cm

A/q the height of image (hi) = height of object (ho)

therfore object should be placed on the centre of curvature ( C) because

• At C hi = ho
• At C v = u

Answer 2

$\large\mathfrak\pink{Answer✓}$

(d) more than 30 cm in front of the mirror

$\large\mathfrak\pink{Explanation✓}$

Here f= 15,

→Radius of curvature is double the focal length

hence, c=30

When an object is placed on c, its image is of the same size, inverted and is formed on c.