Question

The lens used in spectacles for the correction of short-sightedness is a
(A) Concave lens
(B) Convex lens
(C) Plano-convex lens
(D) None of these

Answer 1

Hint:Here we have to first know what is meant by myopia or short sightedness.Myopia is a normal state of vision in which we can easily see objects around us, but fuzzy objects further away. It happens when our eye structure allows rays to bend wrongly, reflecting images on our retina rather than in front of our retina.

Complete step by step answer:
-If the eyeball is too lengthy or the cornea is too curvy then myopia occurs. The light entering the eye is not properly centred as a result and distant objects appear distorted. High myopia is a more serious form of the condition, where the eyeball grows more than it is meant to grow and becomes very long from the front to the back. It can also increase our chance of having other conditions such as detached retina, cataracts and glaucoma in addition to making it hard to see things at a distance. The symptoms of myopia are headaches, squinting, eye strain, eye fatigue etc.
Far point of an eye: When the eye’s accommodation is fully comfortable, the point farthest from the eye at which an object is distinctly centred on the retina. The far point of a person suffering from myopia is less than infinity. In myopia, the individual is able to clearly see near objects, but distant objects are not visible. In eyeglasses that correct nearsightedness, concave lenses are used. Placing concave lenses in front of a nearsighted eye decreases the light refraction and the focal length is increased.

Hence, option A is correct.

Note:Lenses having negative power will extend the focus of a myopic person and give them a good vision. The higher the power of the lens the more far point can be achieved for the eye.