Question

a person needs a lens of power -4.5 dioptre for correction of her vision what is focal length and nature of lens

Answer 1

P=100/ f (in cm)
-4.5= 100 / f
-4.5f = 100
f = 100/ - 4.5
f= - 22.22 cm or 0.22 m

nature of lens- it is a concave lens as focal length is negative so it is a diverging lens.

hope it helps.