Optics Question 418
Question: In a terrestrial telescope, the focal length of objective is 90 cm, of inverting lens is $ 5cm $ and of eye lens is $ 6cm. $ If the final image is at 30 cm, then the magnification will be
[DPMT 2001]
Options:
A) 21
B) 12
C) 18
D) 15
Show Answer
Answer:
Correct Answer: C
Solution:
$ m=\frac{f _{o}}{f _{e}}( 1+\frac{f _{e}}{D} )\Rightarrow m=\frac{90}{6}( 1+\frac{6}{30} )\Rightarrow m=18 $
