Question

What is the focal length of a convex lens of object distance -40 and image distance +40

Answer 1

Answer:

Given that -

object diatance ( U ) = -40 cm

image distance ( V ) = + 40 cm

foxal length ( F ) = ?

By Lens formula ,

1 / F = 1 / V - 1 / U

1 / F = 1 / 40 - ( 1 / - 40 )

1 / F = 2 / 40 = 1 / 20

F = + 20 cm...

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