Optics Question 655

Question: We combined a convex lens of focal length f1 and concave lens of focal lengths f2 and their combined focal length was F. The combination of these lenses will behave like a concave lens, if

[KCET 2000]

Options:

A) f1 > f2

B) f1 < f2

C) f1 = f2

D) f1 $ \le $ f2

Show Answer

Answer:

Correct Answer: A

Solution:

$ F=\frac{f _{1}f _{2}}{f _{2}-f _{1}}, $ F will be negative if $ f _{1}>f _{2} $



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