Question

what is meant by power of lens . write is SI unit. a student uses the lens of focal length 40 cm and another of - 20 CM .write the nature and the power of lens​

Answer 1

Degree of convergence or divergence of lens is known as power of lens.It is also the reciprocal if focal length i.e

P=1/f

IT'S SI UNIT IS DIOPTRE D.

F= 40cm

P=1/40=2.5D

F=-20cm

P=1/-20

=-5D

Answer 2

$\huge\underline{Answer}$

$<b>Power of lens</b>$-

The ability to converge or diverge a ray of light is known as power of lens.

Power of lens 1=

$\frac{1}{focal \: length}$

=

$\frac{1}{0.4}$

=2.5 Diapther.

Nature-Convex lens

Power of lens 2=

$\frac{1 }{ - 0.2}$

=-5 Diapther.

Nature-Concave lens.

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