Question

an object is placed 20 cm from a convex lens whose focal length is 20cm . what is the distance.


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Answer 1

Explanation:

Just to be different, let’s answer using Newton’s lens law: XX’=f^2

So X is the distance from the object to the front focal point, X’ is from the rear focal point to the image. Then

X = 20–20 = 0.

X’ = f^2/X = 20^2/10 =40

The lens to image distance is f + X’ = 20+ 40 =60 cm

hope this helps u