Lenses

Lenses are materials that are curved in order to change the way light passes through. Lenses occur in nature and technology.

A selection of different types of lenses. image: wikipedia

Within optical and visual technology, lenses are optical elements designed to bend light usually to either focus light to a focal point or disperse light or some variation between the two. Combinations of lenses are used to achieve specific goals in dealing with often specific wavelengths of light. 



500px-Concave_lens

Concave lenses tend to create divergent(spread out) beams of light. image: wikipedia


500px-Large_convex_lens

Convex lenses tend to converge or focus light beams to a point. image: wikipedia



Using combinations of lenses can be used to 'bring colours' together. This is useful in microscopes and zoom lenses to avoid a rainbow effect around viewed objects. image : wikipedia



see also: http://en.wikipedia.org/wiki/Lens_(optics)