What is meant by power of lens? State its SI unit. What do their positive and negative signs indicate?

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Solution

The power of a lens is the measure of its ability to converge or diverge a parallel of light on refraction it $.$ Negative sign for concave lensa and positive sign for convex lens $.$ The $S I$ unit of power is dioptre $(D) .$
$f = 1 m$

$P = \frac{1}{1} m = 1 m - 1 = 1 d i o p t r e (D)$

$P = \frac{1}{f} (i n m) = \frac{100}{f} (i n c m) .$

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What is meant by power of lens? State its SI unit. What do their positive and negative signs indicate?

The power of a lens is the measure of its ability to converge or diverge a parallel of light on refraction it. Negative sign for concave lensa and positive sign for convex lens. The SI unit of power is dioptre (D).f=1mP=11m=1m−1=1dioptre(D)P=1f(inm)=100f(incm).