What is meant by the power of the lens? A student uses a lens of focal length 40cm and another -20 cm. Write the nurture and power of each lens.

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Here the convex lens has positive focal length and the concave lens has negative focal length .
Power of convex lens = P1 = 100 / 40 = 2.5 D
Power of concave lens = P2 = 100 /(-20) = - 5 D


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Power of a lens is its capability to converge or diverge light rays incident on it.

The first lens is Convex and has a power of 2.5D
The second lens is Concave and has a power of -5D
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