Question

An object is placed 21 cm from a concave lens of focal length 25 cm. what is the magnification?

Answer 1

The magnification is 0.54

Given,

The distance between object and concave lens, u = -21 cm

Focal length of the concave lens, f = -25 cm

Let m be the magnification.

m = v/u

Here v is the position of image.

We have to find v first.

By using lens equation we can determine v.

That is,

1/f = 1/v – 1/u

So,

- (1/25) = 1/v – (-1/21)

- (1/25) = 1/v + 1/21

1/v = - (1/25) – 1/21

1/v = (-25 – 21) / (21 x 25)

1/v = - (46/525)

Therefore v = - (525/46)

   v = -11.41 cm

Now we have to find magnification, m.

m = v/u

   = (-11.41) / (-21)

   = 0.54

Here magnification is 0.54

Learn more about concave lens here: brainly.com/question/12944945

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