Optics Question 647
Question: A convex lens of power + 6D is placed in contact with a concave lens of power ? 4D. What is the nature and focal length of the combination
[AMU (Engg.) 1999]
Options:
A) Concave, 25 cm
B) Convex, 50 cm
C) Concave, 20 cm
D) Convex, 100 cm
Show Answer
Answer:
Correct Answer: B
Solution:
$ P=P _{1}+P _{2}\Rightarrow P=+6-4=+2D. $
So focal length $ f=\frac{100}{2} $ = + 50 cm; convex lens
