Optics Question 616

Question: Two thin lenses of focal lengths $ f _{1} $ and $ f _{2} $ are in contact and coaxial. The combination is equivalent to a single lens of power

[MP PET 1996, 98; MP PMT 1998; DCE 2000; UP SEAT 2005]

Options:

A) $ f _{1}+f _{2} $

B) $ \frac{f _{1}f _{2}}{f _{1}+f _{2}} $

C) $ \frac{1}{2}(f _{1}+f _{2}) $

D) $ \frac{f _{1}+f _{2}}{f _{1}f _{2}} $

Show Answer

Answer:

Correct Answer: D

Solution:

$ P=\frac{1}{F}=\frac{f _{1}+f _{2}}{f _{1}f _{2}} $



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