Question

V* 1 point A concave lens of focal length 5 cm. the power of lens is (a) 20 D (b) 20 D (c) 90 D (d) -5D Ο Α Ов​

Answer 1

Answer:

-20 D

Explanation:

since f is -ve power is also -ve

refer attachment

hope this helps you

Answer 2

Given:

A concave lens of focal length 5 cm.

To find:

Power of lens ?

Calculation:

• Power of lens is defined as the diverging or converging power of any lens.

• It is the reciprocal of focal length.

• Here focal length of concave lens will be -5 cm.

$P = \dfrac{1}{f(in \: metres)}$

$\implies P = \dfrac{100}{f(in \: cm)}$

$\implies P = \dfrac{100}{ - 5}$

$\implies P = - 20 \: D$

So, power of lens is -20 D.