Geometric optics refers to those optical phenomena that are effectively described in terms of light rays, which travel along straight lines unless deviated by lenses or mirrors. Phenomena such as diffraction, polarization, and interference, which illustrate the wave properties of light, and fluorescence, phosphorescence, and amplification by stimulated emission (as in lasers), which illustrate quantum properties of light, are discussed in Chapter 2.
The basic principles of geometric optics can be summarized in 4 simple rules:
Light rays travel in straight lines through uniform media.
The paths of light rays can be altered only by reflection (when they encounter a smooth reflective surface, such as a mirror) or by refraction (when they travel at different speeds from one medium to another), according to the law of reflection and Snell’s law, respectively.
When light rays pass through more than one refractive surface, the image formed by each surface in turn becomes the source object for the action of the next refracting surface the rays encounter.
The paths of light rays are reversible.
The basic ideas of refraction with lenses were introduced in Part 1 of the Quick-Start Guide. If you are not familiar with this material, it would be helpful to review that chapter now, before proceeding with the more detailed treatment provided here.
Excerpted from BCSC 2020-2021 series : Section 3 - Clinical Optics. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.