Lens (optics): Difference between revisions

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A lens is a clear (transparent) object (like glass, plastic or even a drop of water) that changes the way things look by bending the light that goes through it. They may make things appear larger, smaller, or upside-down. Some places lenses are used include spectacles (eyeglasses), contact lenses, cameras, projectors, microscopes, telescopes, magnifying glasses, etc. Each eye also has a lens.

They work by refraction, or the bending of light.

Lenses have three main shapes. Each different shape changes the image (making it bigger or smaller). The three types are:

Convex: the center part is thicker
Concave: the center part is thinner
Planar: flat

The power of a lens is the reciprocal of its focal length: P = 1/focal length.

History

The word "lens" comes from the Latin word for "lentil," because the earliest convex lenses in common use were shaped like the bean.

The oldest written record of lenses is in the ancient Greek play by Aristophanes called "Clouds", where lenses were used with sunlight to make fire.

Galileo Galilei is commonly believed to have used lenses to make the first known refracting telescope. However, he merely adapted and improved a design he learned from Dutch lensmakers such as Hans Lippershey. He was probably the first to use telescopes to make accurate astronomical observations, though.

Related pages

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@@ Line 1: / Line 1: @@
-[[File:BiconvexLens.jpg|thumbnail|200px|Lens]]
+[[File:BiconvexLens.jpg|thumbnail|upright|Lens]]
-A '''lens''' is a clear ([[transparency|transparent]]) object (like [[glass]], [[plastic]] or even a drop of water) that changes the way things look by bending the light that goes through it. They may make things appear larger, smaller, or upside-down. Some places lenses are used include spectacles ([[eyeglasses]]), contact lens, cameras, projectors, microscopes, telescopes, magnifying glasses, etc. Eyes are also considered lenses.
+A '''lens''' is a clear ([[transparency|transparent]]) object (like [[glass]], [[plastic]] or even a drop of water) that changes the way things look by bending the light that goes through it. They may make things appear larger, smaller, or upside-down. Some places lenses are used include spectacles ([[eyeglasses]]), contact lenses, [[cameras]], projectors, [[microscope|microscopes]], [[telescopes]], magnifying glasses, etc. Each [[eye]] also has a [[lens (eye)|lens]].
 They work by [[refraction]], or the bending of light.
 Lenses have three main shapes. Each different shape changes the image (making it bigger or smaller). The three types are:
-* [[Convex lens|Convex]]: the center part is thicker
+* [http://en.wiktionary.org/wiki/convex Convex]: the center part is thicker
-* [[Concave lens|Concave]]: the center part is thinner
+* [http://en.wiktionary.org/wiki/concave Concave]: the center part is thinner
 * Planar: flat
+The power of a lens is the reciprocal of its [[focal length]]:
+P = 1/focal length.
 == History ==
-[[File:Lentils red and brown.jpg|thumb|250px|Red and brown comparison]]
+[[File:Lentils red and brown.jpg|thumb|Red and brown lentils]]
-The word "lens" comes from "lentil," because the earliest lenses in common use were shaped like the bean.
+The word "lens" comes from the Latin word for "[[lentil]]," because the earliest [http://en.wiktionary.org/wiki/convex convex] lenses in common use were shaped like the bean.
+The oldest written record of lenses is in the [[Ancient Greece|ancient Greek]] play by [[Aristophanes]] called "Clouds", where lenses were used with sunlight to make fire.
+[[Galileo Galilei]] is commonly believed to have used lenses to make the first known refracting [[telescope]]. However, he merely adapted and improved a design he learned from [[Dutch people|Dutch]] lensmakers such as Hans Lippershey. He was probably the first to use telescopes to make accurate [[Astronomy|astronomical]] observations, though.
-The oldest written records of lenses are in the [[Ancient Greece|ancient Greek]] piece of Aristofan called "Clouds", where lenses were used with sunlight to make fire.
-[[Galileo Galilei]] made glass lenses into the first known telescope.
-== Other pages ==
+==Related pages==
 * [[Camera lens]]
 * [[Focal length]]