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Convex lens use – Glasses

When people have a weakness in the lens of their eye that causes hyperopia, or long-sightedness (the ability to see things in the distance but not close up), they will need spectacles, or glasses. To correct this problem they will need a glass lens which is convex.

Ray diagram of a hypermetropic eye forming an image behind the retina

In a hypermetropic (longsighted) eye, the image would form behind the retina; instead, an out of focus (blurred) image forms on the retina.

Ray diagram showing how a convex lens used in glasses can correct a hypermetropic eye

To correct a hypermetropic eye, a convex lens is used to bring the image focused on the retina (the sensory membrane that lines the back of the eye).

Pair of glasses

Another great use of convex lenses.

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