An optical instrument is a device that uses a lens or lenses to create an image of an object. A lens is a piece of transparent material that is shaped such that it bends parallel rays of light. The shape of a lens is a segment of a sphere or a plane. The bending of light causes the light to cross, forming an image. This image can be larger or smaller than the actual object being viewed through the lens. The bending of light as it passes through a medium such as glass or plastic is called refraction. The early Greeks used lenses in magnifying glasses long before the ideas of refraction were understood. One of the first optical instruments was a pair of eyeglasses, invented in Italy in the late 1200s. The telescope was invented in 1608 by the Dutch optician Hans Lippershey. Today, lenses are...