Oscillating E Field Interpretation of Light

I don't know how to explain the classical view of an EM wave quantum mechanically. First off, when you see the graphical representation, there is an E field (x-axis) and a B field (y-axis) oscillating in parallel. Parallel to both of those is the direction of motion (z-axis).







So the z-axis is in units of meters I'm guessing, but what about the x and y axes? Are they just the intensity of the field, so coulombs/newtons and teslas? If so, wouldn't varying field strengths just translate to more/less photon density? Are photons popping into and out of existence periodically?



Also, by this model, the strength of the E or B field depends on the time you absorb it, given its sinusoidal nature. Could someone clear this up for me?



Thanks a bunch!!