Once again but this time in chunks!

Photons and reflection, refraction and spreading

It is important to recognise that the light-as-photons model applies to the various phenomena discussed in episode 01, including reflection, refraction and the spreading of light from a source. They all involve emission and absorption: it's these two processes that require the photon model.

For example, in the case of the light spreading from a source, we might now picture what is going on in terms of streams of photons spreading out in all directions. The fact of the matter is that the intensity of the light beam will still decrease in magnitude according to an inverse square law with distance. The butter gun analogy still works for photons travelling out through space, but please remember that this is just a picture to help us.

Photons behave as they do: we have to try to describe that in the most helpful way. Find more about this in the Physics Narrative.

Teacher Tip: Photons shift energy in drips, not in a stream. Energy is shifted droplet by droplet.