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}} $
