most everyone is familiar with the atomic spectra of gases as observed using a gaseous discharge tube and prism or diffraction grating. When light from the gaseous discharge is passed through a slit and observed with a prism or grating, one sees a few colors appearing as intense isolated parallel lines when each line is an image of the slit deviated through as angle which is dependent on the frequency of the light forming the image. The wavelengths are characteristic of the element emitting the light. For example, the hydrogen spectrum as shown in figure 1 always gives a set of lines in the same wavelength position.