Question

a convex lens of focal length 30cm, a concave lens of focal length 120cm, and a plane mirror are arranged as shown. for an object kept at a distance of 60cm from the convex lens, the final omage , formed by the combination, is a real image, at a distance of​

Answer 1

Answer:

Please provide image/diagram

Answer 2

The final image distance is at 60 cm from the concave lens. This image will be formed behind the mirror.

Explanation:

Given that,

Focal length of convex lens = 30 cm

Focal length of concave lens = 120 cm

Object distance = 60 cm

Suppose the distance between the convex lens and concave lens is 20 cm.

We need to calculate the image distance

Using formula of lens

$\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

Put the value into the formula

$\dfrac{1}{30}=\dfrac{1}{v}+\dfrac{1}{60}$

$\dfrac{1}{v}=\dfrac{1}{30}-\dfrac{1}{60}$

$\dfrac{1}{v}=\dfrac{1}{60}$

$v=60\ cm$

We need to calculate the image distance

Using lens formula again

$\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$

Put the value into the formula

$-\dfrac{1}{120}=\dfrac{1}{v}+\dfrac{1}{40}$

$\dfrac{1}{v}=\dfrac{1}{120}-\dfrac{1}{40}$

$\dfrac{1}{v}=-\dfrac{1}{60}$

$v=-60\ cm$

Hence, The final image distance is at 60 cm from the concave lens. it will be formed behind the mirror.

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Topic : Optics

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