A boy who is suffering from eye defect has been given a prescription as -2D. Based on the information given, answer the question.
Write the nature and focal length of the lens.

Explanation

Nature of the lens:
The lens is biconcave lens.
It is thin at the middle and thicker at the edges.
Focal length of the lens.
Given that power is -2D.
P = `(100)/(f)` (in cm)
(or) `f= (100)/(P) = (100)/(-2) = -50 cm`
`therefore`Focal length (f) = -50 cm.