That branch of optics that illustrates the theory in which q
is substituted for sinq
in Snell's law. Effective results are achieved if the aperture and field angle are made very small. The discrepancy between the image found by this theory and an actual image designates the imperfection in a lens. Also called paraxial optics and first-order optics. 2.
The analysis of the properties of a Gaussian beam.