This is not going to be on the test. However, there was a question about it and this video is pretty good.
Also, there was a question about photons. Basically, there are two models for light: light as a wave and light as a particle. The particle model for light really isn’t needed. Almost all of the effects we see with light can be explained using the wave model of light and a quantum model for matter. I don’t think I should go into any more details – it gets a bit complicated.