NEET Solved Paper 2016 Question 32
Question: A astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance :-
Options:
A) 37.3 cm
B) 46.0 cm
C) 50.0 cm
D) 54.0 cm
Show Answer
Answer:
Correct Answer: D
Solution:
- Using lens formula for objective lens $ \frac{1}{v _0}-\frac{1}{u _0}=\frac{1}{f _0}\Rightarrow \frac{1}{v _0}=\frac{1}{f _0}+\frac{1}{u _0} $
$ \Rightarrow $ $ \frac{1}{v _0}=\frac{1}{40}+\frac{1}{-200}=\frac{+5-1}{200} $
$ \Rightarrow $ $ v _0=50,cm $ Tube length $ \ell =,|v _0|+f _{e}=50+4=54,cm. $
