Question

1.A real image, 1/5 th size of object is formed at a distance of 18 cm from
a mirror. What is the nature of the mirror ? Calculate its focal length.​

Answer 1

Answer:

Nature of mirror is Concave since it's forming Real image.

Focal length = -15cm

Explanation:

H' = 1/5H

5H'= H

using magnification

H'/H = -v/u

H'/5H' = -(-18)/u

u = 18 * 5

u = 90

using mirror formula

1/F = 1/V + 1/U

1/F = -1/18 + (-1/90)

1/F = (-5-1)/90

1/F = -6/90

F. = -15 cm