Question

A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads : Left eye : + 2.50 D Right eye : + 2.00 D

(a) State whether these lenses are thicker in the middle or at the edges.

(b) Which lens bends the light rays more strongly ?

(c) State whether these spectacle lenses will converge light rays or diverge light rays.

Answer 1

(a) These lenses have positive powers and hence positive focal lengths, so they are convex lenses. Convex lenses are thicker in the middle.

(b) Lens of greater power bends light rays more quickly. So, +2.50 D lens bends light rays more quickly.

(c) These spectacle lenses will converge the light rays because these are convex lenses.