Abstract
The main theme is a tutorial presentation of the major effects of atmospheric turbulence on the phase and frequency of electromagnetic waves in the optical spectrum. The emphasis is not on a comprehensive review, but rather on the tutorial aspect. Starting from fundamental principles, all significant results are derived by simple physical reasoning and are compared to existing ones in the literature. Unlike classical reviews, some of the more important results that pertain to coherent optics, in particular laser heterodyning, are derived and discussed. Finally, an attempt is made to compare optical phase fluctuations with fluctuations in other portions of the electromagnetic spectrum.