To determine that light behaves as a wave, scientists conducted several experiments but none were as famous as the double-slit experiment. In this experiment, light was shown through two small slits and projected onto another screen. If light only acted as a particle, it was to be expected that the screen would show two distinct bright patches of light from where it had shown through the slits. However, the screen had multiple areas of light shining on it. The only explanation for this was to assume that light could also act as a wave where the light waves that came through the first slit interacted with the waves from the second slit creating wave interference (Jacobs, G. & Schulman, J., 2005). Interference is a defining characteristic of waves; particles cannot interfere with one another. See Figure 1 below to demonstrate the outcome of the double slit experiments: