The image obtained with a convex lens is erect and its length is `4` times the length of the object. If the focal length of lens is `20 cm`, calculate the object and image distances.
Text Solution
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Here, `f = 20cm, m = +4`, for correct image. From `m = (f)/(u + f)` `4 = (20)/(u + 20) , u = - 15cm` From `m = (f - v)/(f)` `4 = (20 - v)/(20) , v = - 60 cm`
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