This is a diagram of the double-slit experiment. A light source (represented by a light bulb) sits on the left hand side. The light waves are then depicted as they approach a barrier on the right, which has two slits in it. The waves pass through these slits and continue to travel until they hit the screen. A rectangular strip notated with ‘appearance of screen’ shows a pattern of black and white stripes, with patches of grey blending the space between them.