Optics Question 636
Question: The focal length of a combination of lenses formed with lenses having powers of + 2.50 D and - 3.75 D will be
[RPMT 1997]
Options:
A) - 20 cm
B) - 40 cm
C) - 60 cm
D) - 80 cm
Show Answer
Answer:
Correct Answer: D
Solution:
$ P=P _{1}+P _{2}=2.50-3.75=-1.25D $ .
So $ f=\frac{100}{1.25}=-80 $ $ cm $
