Lens (optics)
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. Eyes are also considered lenses.
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:
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 records of lenses are in the ancient Greek piece of Aristofan called "Clouds", where lenses were used with sunlight to make fire. Galileo Galilei is commonly believed to have made the first known refracting telescope, but he merely adapted and improved a design he learned from Dutch lensmakers such as Hans Lippershey.
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