Optics Question 390
Question: In Gallilean telescope, if the powers of an objective and eye lens are respectively +1.25 D and ? 20 D, then for relaxed vision, the length and magnification will be
Options:
A) 21.25 cm and 16
B) 75 cm and 20
C) 75 cm and 16
D) 8.5 cm and 21.25
Show Answer
Answer:
Correct Answer: C
Solution:
$ f _{o}=\frac{1}{1.25}=0.8m $ and $ f _{e}=\frac{1}{-20}=-0.05m $
$ |{L _{\infty }}|=|f _{o}|-|f _{e}|=0.8-0.05=0.75m=75cm $
and $ |{m _{\infty }}|=\frac{f _{o}}{f _{e}}=\frac{0.8}{0.05}=16 $
