#### Question

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

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#### Solution

Focal length of concave lens (OF_{1}), *f* = – 15 cm

Image distance, *v*= – 10 cm

According to the lens formula,

`1/v-1/u=1/f`

`1/u=1/v-1/f`

`=-1/10-1/-15=-1/10+1/15=-5/150`

`u=-30 cm`

The negative value of *u* indicates that the object is placed 30 cm in front of the lens. This is shown in the following ray diagram.

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Solution for question: A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram. concept: Refraction of Light - Image Formation in Lenses Using Ray Diagrams - Concave Lens. For the course CBSE