Question

if a mirror forms image of an object placed at infinity at 10 cm what its focal length​

Answer 1

Explanation:

Since it is a convex mirror, therefore u= -ve and since the image is formed behind the mirror, therefore v= +ve.

The formula for mirror is-

1/v + 1/u = 1/f

1/f = 1/5 + 1/-10

1/f = 1/5 - 1/10

1/f = 2–1/10

1/f = 1/10

f = 10cm

Therefore, the focal length of the convex mirror is 10cm.