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 biconvave 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.