Question

find the focal length of a lens of power -2. 0D.what type of lens is this?​

Answer 1

Given:

Power of lens is -2.0 D.

To find:

• Focal length
• Type of lens

Calculation:

• The power of lens is -2 Dioptres.

So, let focal length be f :

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

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

$\implies \: f= \dfrac{100}{P}$

$\implies \: f= \dfrac{100}{ - 2}$

$\implies \: f= - 50 \: cm$

Since the focal length is negative, the lens is CONCAVE LENS.