A converging lens is kept co-axially in contact with a diverging lens – both the lenses being of equal focal lengths.
A converging lens is kept co-axially in contact with a diverging lens – both the lenses being of equal focal lengths. What is the focal length of the combination?
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Let focal length of converging and diverging lenses be + f and - f respectively.
Power of converging len P1 = 1/f, Power of diverging lens P2 = - 1/f
∴ Power of combination P = P1 + P2 = 1/f - 1/f = 0
∴ Focal length of combination F 1/P = 1/0 = ∞ (infinite)
F = ∞.
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