Question

A student needs spectacles of power - 0.5d for the correction of his vision . Name the defect

Answer 1

Eyes are spectacular organs. They can accommodate varied object distances and yet form images on the retina of same distance. This is because, Eyes has ciliary muscles which help to change the focal length. When eyes loses it power to accommodate, We call such as eye defects. Spectacles with specific lens can help to overcome these defects!


We know that, Focal length of concave lens is negative while focal length of convex lens is positive.

So, Given power = - 0.5 d.

Therefore, He requires concave lens. We know that, Concave lens is used to correct Myopia.

The student is having defect of Myopia.

Focal length = 1 / Power

= 1 / -0.5

= - 2m

= - 200cm

Answer 2

myopia (Short Sightedness).