# How are power and focal length of a lens related ? You are provided with two lenses of focal length 20 cm and 40 cm respectively. Which lens will

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How are power and focal length of a lens related ? You are provided with two lenses of focal length 20 cm and 40 cm respectively. Which lens will you use to obtain more convergent light ?

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P = (1)/(f).
For obtaining more convergent light, power of lens must be larger. Therefore, its focal length must be smaller, Therefore, the lens of f = 20 cm will provide more convergent light.