Ray Optics And Optical Instruments Ques 36

36. A convex lens and a concave lens, each having same focal length of $25 $ $cm$, are put in contact to form a combination of lenses. The power in diopters of the combination is

[2006]

(a) $50$

(b) infinite

(c) zero

(d) $25$

Show Answer

Answer:

Correct Answer: 36.(c)

Solution:

  1. (c) From the formula,

$\frac{1}{f}=\frac{1}{f_1}+\frac{1}{f_2}=\frac{1}{25}-\frac{1}{25}=0$

Power of combination $=\frac{1}{f}=0$

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