One exhibit showing interference and diffraction of light, containing:- Young's interference fringes. Fresnel's interference fringes. Diffraction at a straight edge. Diffraction by a solid obstacle. Consisting of 2 optical benches and 8 sliding stands, 2 metal test objects, 1 photographic object, 1 Fresnel biprism, 4 convex lenses 38mm diameter 120. dioptres.