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What are concave lenses used for?
North Penn HS, Lansdale, PA
For a great explanation of how concave (and convex) lenses work, check out the answer to the question Light rays through lenses
Concave lenses work to make something look smaller, so they’re not quite as common as convex (magnifying) lenses. But they’re still used in a lot of different things. For example, eyeglasses have one convex surface and one concave surface. Between the two, the glasses can bend the light just the right amount before it gets to your eyes.
Convex lenses have "aberrations", which means that they don't focus light of different colors or from different directions quite where they need too. A combination of a convex lens and a concave lens made from a different type of glass can approximately get rid of the "chromatic aberration"- the problem of focusing light of different colors differently. Thus concave-convex combinations are used in many high quality telescopes and binoculars so that the images at different colors aren't shifted from each other.
Hope this helps!
(republished on 07/29/06)
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