Why does the double slit experiment prove the wave-like properties of EM radiation? The double slit experiment is set up so that we have a light source pointed at two vertically parallel slits in a medium and another flat medium behind it to observe the effects of the light. If light were made of particles, when the light shines through the double slits, one would expect the image on the other side to have much of the same relative shape and size of the slits, however, that is not what occurred. Instead of slits, a sequence of dark and bright bands of light appeared on the other side of the slits, exhibiting a pattern of interference, a distinctly wave-like property.