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How do glasses work?
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The lens in the eye of a person with normal eyesight focuses light rays onto the retina at the back of the eye. A farsighted person has an eyeball that is too short when measured front to back. Glasses to correct the condition have convex lenses, which focus light rays onto the retina instead of behind it. A nearsighted person's eyeball is too long front to back. Glasses to correct nearsightedness have concave lenses, which focus light rays correctly onto the retina instead of in front of it. | | Different kinds of lenses are used to correct far-sightedness and near-sightedness. |
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Previous:
Back
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Book:
1001
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Section:
Science and Technology
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Chapter:
Heat and Light
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