Comparing the Experiments

You have now completed three two-slit experiments. One each with light, waves and particles. From the results of these experiments can you see why Young concluded that light behaved as a wave?

Compare the pattern you observed for laser light passing through two slits with the patterns you obtained for waves and particles. As you see with these experiments, interference - the pattern of light and dark for light - only occurs for waves. Particles can't do it.

The diagram below illustrates graphically how the wave nature of light results in an interference pattern from two slits.