Question

What is farsightedness or hypermetropia?

Answer 1

Hint: We humans can see the objects in front of us because of our eyes. Our eye behaves as a convex lens of refractive index equal to 1.437. As the human eye grows older, it suffers from a number of defects like myopia, hypermetropia.

Complete step-by-step answer:
We humans can see the objects in front of us because of our eyes. Our eye behaves as a convex lens of refractive index equal to 1.437.
The outer layer of the eye consists of the cornea. Light enters our eye through the cornea. Behind the cornea there is a convex lens that helps to focus the rays of light coming from the object on a light sensitive membrane called the retina. Thus, an image of the object is formed on the retina. Then a message about the image is sent through nerve impulses and this is interpreted by the brain. This is how we can see the in front objects.
However, as we get older, our eyes get defected. One of the eye defects is far sightedness. This defect is also called hypermetropia.
When a person is suffering from hypermetropia, he can see the distant objects (far away objects) clearly but the objects that are nearer are not clearly visible. To see an object clearly, the image of the object must be formed on the retina. However, when the person is suffering from hypermetropia, the image of the object which is near to the eye is formed behind the retina. Due to this reason, the person cannot see the near objects clearly.
The reasons for the image to be formed behind the retina can be an increase of the focal length or radii of curvature of the lens in our eye or it can also be if the distance between eye lens and retina decreases.

Note: Hypermetropia or farsightedness is a partial blindness of a person. This defect can be corrected by using an appropriate lens. As we know, in hypermetropia, the image is formed behind the retina of the eye. So, if the person wants to see the object clearly then the image must be formed on the retina. For this, we can use a convex lens of a specific focal length such that the rays are more converged or brought together so that they intersect exactly on the retina.