Young and Fresnel without sodium lamp

摘要

The well - known experiment of Young about interferences by means of a Fresnel biprism to obtain the double - slit is usually made using quasi - monochromatic sources: a sodium spectral lamp, a laser, etc. Besides , a monochromatic source is also assu med in order to develop the theoretical explanation of the experiment. The n , some experimental details are lost, as the dependence of the fringe - to - fringe spacing on the wavelength. Moreover, a much more dangerous negative effect is originated, since some students come to the following false conclusion: interference p henomena only are originated by monochromatic sources. In this paper, an easy modification of this experiment is shown. Thus, by employing a white source and RGB filters, it is possible to obse rve interference fringes with polychromatic light and verify that its period raises with the wavelength.