Question 27 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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The power (P) and focal length (f) of a lens are related by the following equation P=1f Power of a lens is inversely proportional to its focal length therefore lens having focal length of 20 cm will provide more convergence.