Optics Question 636

Question: The focal length of a combination of lenses formed with lenses having powers of + 2.50 D and - 3.75 D will be

[RPMT 1997]

Options:

A) - 20 cm

B) - 40 cm

C) - 60 cm

D) - 80 cm

Show Answer

Answer:

Correct Answer: D

Solution:

P=P1+P2=2.503.75=1.25D .

So f=1001.25=80 cm



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