Question

the power of lens is 2.5 dioptre . what is the focal length and the type of the lens?
plsss gibe me answer

Answer 1

Power = +2.5 D

F = 1/P = 1/2.5 = 0.4m = +40cm

Focal length is 40cm and it is a convex lens.

Answer 2

Given:

• Power of lens = 2.5 Dioptre

To find:

• Type of lens ?
• Focal length of lens ?

Calculation:

Since the sign of power is positive, we can confidently say that the lens is a CONVEX LENS.

• Convex lens are converging lens which are able to converge parallel rays of light towards the focus.

Now, let focal length be f :

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

$\implies\: 2.5= \dfrac{1}{f}$

$\implies\: f= \dfrac{1}{2.5}$

$\implies\: f= 0.4 \: metres$

$\implies\: f= 40 \: cm$

So, focal length of lens is 40 cm.