Which lens is used by people having short-sight?
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convex
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concave
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plain
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cancavo-convex
Short-sightedness (myopia) occurs when the eye focuses light in front of the retina. Concave lenses diverge light rays before they enter the eye, shifting the focal point back onto the retina. Convex lenses are used for long-sightedness (hyperopia).
Concave lenses correct short-sightedness (myopia). In myopia, the eyeball is too long (or the cornea too curved), so the eye's lens focuses incoming light in front of the retina instead of on it, making distant objects blurry. A concave (diverging) lens spreads out the light rays before they enter the eye, effectively pushing the focal point back onto the retina. A convex (converging) lens does the opposite and is used for long-sightedness (hyperopia), where the focal point falls behind the retina.