Optics Question 607
Question: Two lenses of power 6D and - 2D are combined to form a single lens. The focal length of this lens will be
[MP PET 2003]
Options:
A) $ \frac{3}{2} $ m
B) $ \frac{1}{4} $ $ m $
C) 4 m
D) $ \frac{1}{8} $ $ m $
Show Answer
Answer:
Correct Answer: B
Solution:
Combined power $ P=P _{1}+P _{2}=6-2=4D $ .
So focal length of combination $ F=\frac{1}{P}=\frac{1}{4}m $
