Optics Question 579

Question: A lens of power + 2 diopters is placed in contact with a lens of power - 1 diopter. The combination will behave like

Options:

A) A convergent lens of focal length 50 cm

B) A divergent lens of focal length 100 cm

C) A convergent lens of focal length 100 cm

D) A convergent lens of focal length 200 cm

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Answer:

Correct Answer: C

Solution:

$ \frac{1}{f}=\frac{1}{f _{1}}+\frac{1}{f _{2}}=\frac{P _{1}}{100}+\frac{P _{2}}{100}=\frac{1}{100}\Rightarrow f=100 $ cm

$ \therefore $ A convergent lens of focal length 100 cm.



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