Question

A convex lens is a focal length 10 cm. what is its power?​

Answer 1

Answer:

Power =1/f

p=1/10

p=0.1 D

Answer 2

Given :-

• A convex lens is of focal length 10 cm

To find :-

• Power of convex lens

Solution :-

At first,

☄Convert 10 centimetres into metres :-

• It is because the power of lens is defined as the reciprocal of its focal length in metres.

$\rm\:f=10\:cm$

$\rm\dashrightarrow\:f=\dfrac{10}{100}\:m$

$\rm\dashrightarrow\:f=0.1\:m$

☯ Putting the above value of focal length in the formula for the power of lens

we know that,

$\blue{\bigstar}\:\:{\underline{\boxed{\bf\red{P=\dfrac{1}{f}}}}}$

$\rm\longrightarrow\:P=\dfrac{1}{0.1}$

$\rm\longrightarrow\:P=\dfrac{1\times\:10}{1}$

$\rm\longrightarrow\:P=10\:dioptres$

Hence,the power of convex lens will be 10 dioptres.

$\orange{\bigstar}\:\:{\underline{\boxed{\bf\purple{More\:Information}}}}$

☯ Related to power of lens :-

➊ A lens of short focal length has more power whereas a lens of long focal length has less power.

➋ The unit of the power of a lens is dioptres which is denoted by letter D.

➌ A convex lens has a positive focal length so,the power of convex lens is positive.