ABSTRACT
This chapter discusses the phenomena of interference and diffraction, and presents some distinctive properties of the light wave. The fringe visibility is related with the coherence. Then Young's experiment and some interferometers are introduced. As an extension of Young's experiment, the diffraction is introduced. A variety of interferometers have been developed in order to measure distances, refractive indices, and so on. In particular, the Fraunhofer diffraction can be represented as the Fourier transform. Some numerical examples of diffraction patterns of simples’ objects are presented. The extent of the diffraction is proportional to the wavelength and inversely proportional to the size of the aperture. The wave expands on a screen located far from the aperture, which is illuminated by a coherent light. The width of the diffraction spot decreases as the number of the slits increases. The width of the envelope of the diffraction pattern becomes wider as the width of the slits become shorter.
