Define power of a lens. What is its unit? One student uses a lens of focal length 50cm and another of -50cm. What is the nature of the lens and its power used by each of them?
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The degree of divergence or convergence achieved by a given lens is called power of the lens. The unit of power of lens is diopter and is expressed by D. Focal length of lens used by first student is in positive hence it is a convex lens. The lens of second student is a concave lens.$\text{P}=\frac{1}{\text{f}}=\frac{1}{0.5}=2$
Power of lens (first student) = +2
Power of lens (second student) = -2
Power of lens (first student) = +2
Power of lens (second student) = -2
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