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Light Reflection and Refraction
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03/12/2020 1:02 pm
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Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of -50 cm. What is the nature of the lens and its power used by each of them?
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03/12/2020 1:03 pm
Power of a lens: The ability of a lens to converge or diverge the light rays is called power (P) of the lens. It is defined as the reciprocal of the focal length, i.e. f = 1/f. The SI unit of power of a lens is dioptre (D). A lens of focal length 100 cm has a power of 1 dioptre, i.e. 1 dioptre = 1 m-1. The lens of focal length +50 cm has a power of +2 D and is convex while the other is having a power of -2 D and is concave.