Optics Question 103
Question: The average distance between the earth and moon is $ 38.6\times 10^{4} $ km. The minimum separation between the two points on the surface of the moon that can be resolved by a telescope whose objective lens has a diameter of 5 m with $ \lambda =6000\ {AA} $ is
[MP PMT 1993]
Options:
A) 5.65 m
B) 28.25 m
C) 11.30 m
D) 56.51 m
Show Answer
Answer:
Correct Answer: D
Solution:
Resolving power $ =\frac{1.22\ \lambda }{a}=\frac{1.22\times 6000\times {{10}^{-10}}}{5} $ Also resolving power $ =\frac{d}{D}=\frac{d}{38.6\times 10^{7}} $
$ \therefore \frac{1.22\times 6\times {{10}^{-7}}}{5}=\frac{d}{38.6\times 10^{7}} $
Therefore $ d=\frac{1.22\times 6\times {{10}^{-7}}\times 38.6\times 10^{7}}{5}m=56.51\ m $
