Fringes formed by white light
Broadly speaking, white light consists of seven different colours, as we saw in chapter 025. So if a white light source is used in Young’s experiment we get seven sets of differently spaced coloured fringes all superimposed on one another. The previous experiment shows that the central fringes for each colour are in the same straight line. The one place where all colours constructively interfere together will therefore be at the central fringe. Consequently this will be white and the
resultant appearance will be a central white band, bordered symmetrically on either side by bands of composite colours due to superposition of the other differently spaced colour fringes.