Question

An object of size 1.5 cm is placed at a distance of 18 cm from a concave mirror of focal length 20 cm find the position size and nature of the image.

Answer 1

Answer:

= -15cm, v = -10cm

f = ?

We know that

1/v + 1/u = 1/f

⇒ 1/(-10) + 1/(-15) = 1/f

⇒ 1/f = -(1/10) – (1/15) = (-3 – 2)/30 = - (5/30) = -(1/6)

∴ f = - 6 cm

∴ The focal length of the concave mirror is 6 cm