A person needs a lens of power –4.5 D for correction of her vision.

(a) What kind of defect in vision is she suffering from?

(b) What is the focal length of the corrective lens?

(c) What is the nature of the corrective lens?

(a) She is suffering from myopia since the power of lens is negative.

(b) Focal length

So, f = 1/(-4.5) = -0.22m = -22cm

So, focal length of the corrective lens should be -0.22m or -22cm.

(c) The corrective lens should be concave in nature.