NEET Solved Paper 2018 Question 10

Question: An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of [NEET - 2018]

Options:

A) Large focal length and large diameter

B) Large focal length and small diameter

C) Small focal length and large diameter

D) Small focal length and small diameter

Show Answer

Answer:

Correct Answer: A

Solution:

For telescope, angular magnification $ \text{=}\frac{{f_0}}{{f_E}} $

So, focal length of objective lens should be large.

Angular resolution $ =\frac{D}{1.22\lambda } $ should be large.

So, objective should have large focal length $ (f _0) $ and large diameter D.