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 axis of the sine wave is the direction of the wave (actually it spreads in a sphere but if you transmit a wave between point A and point B, you only need to consider this line). Along that axis, the wave represents the intensity of electric and magnetic field.
Actual electromagnetic wave is pulsating in a “high electric field/low magnetic field – high magnetic field/low electric field” fashion with fields quickly changing polarities and intensities. But it’s an actual sine wave: electric field intensity can be described as a sin function (of distance or time) while magnetic field intensity will be cos function for the same parameter.
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