Optics Question 410
Question: If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objective
[AFMC 1994]
Options:
A) 100 cm
B) 10 cm
C) 20 cm
D) 25 cm
Show Answer
Answer:
Correct Answer: A
Solution:
$ |m|\ =\frac{f _{o}}{f _{e}}=20 $ and $ L=f _{o}+f _{e}=105 $
$ \Rightarrow f _{o}=100\ cm $
