Question

Question 18 (c)
A person needs a lens of power –4.5 D for correction of her vision.
What is the nature of the corrective lens?

Answer 1

Since the power of the lens is negative, its principal focus is also negative. Therefore concave lens is the corrective lens which the woman will need because concave lens has negative prinicipal focus and power.
Concave lens is used as the corrective lens for a myopic eye.