Optical path

The path that light takes in traversing an optical medium or system is often called the optical path. The physical length of an optical device can be reduced to less than the length of the optical path by using folded optics. The optical path length as defined in optics is the length of the path multiplied by the index of refraction of the medium.

Path of light in medium, or between two media is affected by the following:

‘change in optical length is equal to wavelength of light passed’

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