Question

name the type of lens is - 20D find the focal length of this lens​

Answer 1

Answer:

concave lens coz of -ve power

p=1/f

=-1/20

Answer 2

Explanation:

it is a concave type of lens

the focal length can be found out by the formula

P = 1/f

here f is in meters and the D represent dioptre

so,

P = - 20D

then P = 100/f

here f is in cm

so f = 100/-20

= - 5 cm

f is - 5 cm or - 0.5 m

hope it helps you!❤️