Hyperopia and correction

Hyperopia means long-sighted – i.e, a person can see things clearly in the distance.

Sight long is great

A person who is long-sighted can focus clearly on far objects but cannot focus on near objects. Close objects are blurry.

This is caused by the eye being too short, the cornea being too flat or the power to focus being too weak.

Object image blurry due to being long sighted and not focused on the back of the retina

Hyperopia – light rays focus too far behind the retina. The retina only receives a blurred image.

Here we can see the light is focused behind the retina and not on it which will make the image look blurry.

Hyperopia sight long is great

If it could, the lens would need to get rounder and therefore thicker so that light refracts more. So the problem is as follows:

Convex lens too thin to focus the image

The way to get the image to focus on the screen is to use a convex lens in front of our current convex lens.

Two convex lenses used to focus an image on a screen

The effect of using a convex lens in front of a convex lens is to move the image to the point where it focuses on the screen.

This has exactly the same effect as putting a convex lens in glasses in front of an eye that suffers from hyperopia when you need to see close objects.

Convex lens used in glasses to correct longsightedness

Using a convex lens in a pair of glasses shortens `di` (image distance) to the point where it focuses on the retina.

Summary

Hyperopia
SIGHT LONG is Great
FOCUS LONG
Use convex glasses (lens)