Question

find the position of an object which when placed in front of a concave mirror of focal length 20cm produces a virtual image which is twice the size of an object draw ray diagram pls help

Answer 1

Answer:

Explanation:

Given :-

Focal length, f = - 20 cm

To Find :-

Position of an object.

Formula to be used :-

Mirror formula, i.e 1/v + 1/u = 1/f

Solution :-

Putting all the values, we get

We know that,

M₂/M₁ = 2 = - v/u

⇒ v = 2u

Let assume that u = - x

then, we have v = 2x

By Mirror formula,

1/v + 1/u = 1/f

⇒ 1/2x - 1/x = 1/- 20

⇒ 1 - 2/2x = 1/- 20

⇒ - 1/2x = 1/- 20

⇒ x = 20 cm

That means, u = x = 20 cm

And v = 2x = 2 × 20 = 40 cm.