I see lots of drawings illustrating amplitude, frequency, etc using a sine wave to represent an EM wave, but why are they drawn like this? What do the crests and troughs mean/what values do they represent? And what do these waves look like in real life?
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The waves are mathematical model. They don’t exist in real life for us to “see”. They are also known to be inaccurate, so they can’t even represent a real physical entity.
So what does the model look like? You have a EM field, which is a assignment of a pair of vectors to each point, at each instance in time (so when time change the vectors change).
A pair of vector is difficult to draw, so what happen is that they take just 1 numerical value out of it, such as by projecting 1 vector on an axis. This gives you the vertical axis.
For the horizontal axis, it’s either distance or time. If it’s distance, you’re taking a snapshot at 1 instance in time, and look at all points along an axis in the direction the wave is moving. If it’s time, you’re fixing a single point and look at how the vectors at that point change over time.
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