Question

What is power of lens ? Write its S.I unit​

Answer 1

✏ Power of lens:-

The ability of a lens to converge or diverge the light rays is called power of lens. The more the power of a lens, the more is its ability to refract light that passes through it.

• It's the reciprocal of the focal length of the lens.

$\bf p \propto \: \dfrac{1}{f}$

• P = power of lens
• f = focal length of lens(in meters).

- Power of a convex lens is +ve (positive)

- Power of a concave lens is -ve (negative)

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✏ S.I. unit:-

SI unit of power of lens is Dioptre.

When power of lens has focal length as 1 meter, is known as Dioptre.

$\bf 1 \: dioptre = \dfrac{1}{meter}$

Answer 2

Power of lens is defined as the ability of lens to converge or diverge the light rays falling on it

Or

The reciprocal of focal length of lens is called power of lens

$\boxed{ \sf{Power \: of \: lens \: (P) = \frac{1}{Focal \: length \: (in \: m)} }}$

The SI unit of power of lens is " Dipotre "

The power of lens of convex lens is positive

The power of lens of concave lens is negative

The equivalent power of n lenses in contact is given by

$\boxed{ \sf{P = P_{1} + P_{2} + .. + P_{n} }}$