Question

A concave lens has a focal length of 25cm. it's power in diaptor is​

Answer 1

GIVEN :

Focal Length = -25 cm

We have to find the power of the concave lens.

We know that,

Power = 1/focal length

Power = 1/-25m

Convert 1/-25m into cm

1 metre = 100cm

D = 100/-25

D = -4 diopters

Therefore, the power of the lens is -4diopters.

Diopter is the SI unit of power of the lens.

Answer 2

$\large{\underline{\underline{\mathfrak{Answer :}}}}$

Power of Concave lens is -4 D

$\rule{200}{0.5}$

$\underline{\underline{\mathfrak{Step-By-Step-Explanation :}}}$

Given :

• Focal length is - 25 cm

____________________

To Find :

• Power (in D)

___________________

Solution :

As we know that :

$\large{\boxed{\sf{P \: = \: \dfrac{1}{f}}}} \\ \\ \rightarrow {\sf{P \: = \: \dfrac{1}{-25}}}$

Power, is in Meter. So divide focal length by 100

$\rightarrow {\sf{P \: = \: \dfrac{1}{\dfrac{-25}{100}}}} \\ \\ \rightarrow {\sf{P \: = \: \dfrac{-100}{25}}} \\ \\ \rightarrow {\sf{P \: = \:- 4}} \\ \\ \underline{\sf{\therefore \: Power \: of \: Concave \: lens \: is \: - \: 4D}}$