Magnifying Power and Focal Length of a Lens
A LensIs a clear object, usually made of glass or plastic, which is used to Refract, or bend light. Lenses can concentrate light rays (bring them together) or spread them out. Common examples of lenses include camera lenses, telescope lenses, eyeglasses, and magnifying glasses. Lenses are often Double lenses, meaning they have two curved sides. A ConvexLens is rounded outward, while a ConcaveLens curves inward. (A great way to remember this is that a ConcaveLens creates an indent like a cave!)
The centre axis through a lens is called the Principal axis. On lenses that concentrate light rays, the point at which the rays meet, the Focal point, is located on the principal axis. The distance the focal point is from the surface of a lens is called the Focal lengthOf a lens, and is important when determining the magnifying power of devices like magnifying glasses.
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