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 $



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