Diffraction of polychromatic light
If we use light that’s made up of multiple wavelengths (for example, white light), we’ll see a pattern of coloured fringes instead of just bright and dark fringes.
White light
Section titled “White light”The central fringe will be white, because all of the wavelengths will interfere constructively at the centre.
The fringes on either side of the central fringe will be coloured, because the different wavelengths will interfere constructively at different points on the screen.
Colour of the fringes
Section titled “Colour of the fringes”Closer to the centre, the fringes will be blue and violet, because the shorter wavelengths will interfere constructively closer to the centre.
Further away from the centre, the fringes will be red and orange, because the opposite (longer wavelengths will interfere constructively further away from the centre).