Paraxial approximation: Difference between revisions

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In [[geometric optics]], the '''paraxial approximation''' is ana [[small-angle approximation]] used in [[Ray tracing (physics)|ray tracing]] of light through an optical system (such as a [[lens (optics)|lens]]).<ref name=Greivenkamp>{{cite book | first=John E. | last=Greivenkamp | year=2004 | title=Field Guide to Geometrical Optics | publisher=SPIE | others=SPIE Field Guides vol. '''FG01''' | isbn=0-8194-5294-7 |pages=19–20 }}</ref>

A '''paraxial ray''' is a [[Ray (optics)|ray]] which makes a small angle (''θ'') to the [[optical axis]] of the system, and lies close to the axis throughout the system.<ref name=Greivenkamp/> Generally, this allows three important approximations (for ''θ'' in [[radian]]s) for calculation of the ray's path:<ref name=Greivenkamp/>