I have two questions that are slightly unrelated to each other which has confused me while I was doing revision. So I understand that if waves are transmitted (e.g. radio waves) then some interference would occur and not be able to give perfect result for any experiment conduced so pulses are used. What are pulses? How do they differ to a wave? Also, when talking about polarised light, many question ask to draw how polarised light differs from unpolarised light and I draw it like this: But one mark is awarded for showing vibration and oscillations on the diagram, how do I do that?