If a convex lens of focal length 80 cm a

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Target Exam

CUET

Subject

Physics

Chapter

Ray Optics

Question:

If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power?

Options:

6.5D

-6.5D

7.5D

-0.75D

Correct Answer:

-0.75D

Explanation:

ResultantPower after combining the two lenses

$ P = P_1 + P_2$

$P_1 = \frac{100}{80} = 1.25D, P_2 = \frac{100}{ -50} = -2 D$

$\Rightarrow P = P_1 + P_2 = 1.25 -2 = -0.75D$