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The image obtained with a convex lens is...

The image obtained with a convex lens is erect and its length is four times the length of the object. If the focal length of the lens is 20 cm, calculate the object and image distances.

Text Solution

Verified by Experts

Here f = 20 cm , m = + 4 for a virtual image.
To calculate u, we have
`m=(f)/(u+f)rArr4=(20)/(u+20)rArr=-15cm`
To calculate v, we have
`m = (f-v)/(f) rArr 4 = (20 - v)/(20) rArr v = - 60 cm`
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