ABSTRACT
With the exception of laser sources, interference can be observed only when the two vibrations come from the same source. The wave coming from a source must be divided into two waves capable of interfering. The two general methods are interference by wave-front division, and interference by amplitude division. The illumination on the screen is a result of the super-imposition of various systems of fringes corresponding to different colours. A lamp with a straight vertical filament in front of which coloured filters can be held is placed on a high table. Opaque screens with slits are distributed to the students. Each screen carries three or four pairs of double-slits having different separations.
