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created: 2021-10-26 09:52:57
modified: 2022-01-10 04:13:04
Used in geometric optics, the paraxial approximation is a small-angle approximation used in Gaussian optics and ray tracing of light through an optical system (such as lens).
The paraxial ray is a ray that makes a small angle to the optical axis of the system and lies close to the axis through the whole system.
In this case, the following approximations can be used when calculating the ray's path:
These are first order approximations and the second order approximation is the same except for the cosine: