Hi, I have a question about electromagnetic amplitudes. we can easily find the wavelength of any EM, but how do we determine its amplitude? in terms of joules vs. length vs. frequency?
The square of the amplitude [of the electric field carried by the wave] is proportional to the irradience (intensity) of the wave, which is the power per unit area and hence has SI units of watts per square meter (W.m-2)
The easiest way is to measure the power or irradiance and infer the amplitude from there, assuming of course that the wave is monochromatic, infinite etc. etc.