Discusses the theory and experimental procedures for using Young's eriometer to determine the diameters of blood corpuscles, lycopodium powder, and wool fibers. (CC)

Describes use of a Fresnel biprism to demonstrate double-slit interference with polarized light. Discusses polarization and phase properties of a randomly polarized gas. (JM)

Discusses the production and structure of a sequence of optical crystals which can serve as one-, two-, and three-dimensional diffraction plates to illustrate diffraction patterns by using light rather than x-rays or particles. Applications to qualitative presentations of Laue theory at the secondary and college levels are recommended. (CC)