Any function of the form f(x+ct) or f(x-ct) can be a solution to a wave equation - including the electromagnetic wave equation generated by combining maxwell's equations. Light is an electromagnetic wave which obeys maxwell's equations. If you were to meausure the electric field of light, is it really a sinuoid? Or is it just represented that way for convenience, and because any function can be represented by sinusoids? I understand that any well behaved function can be represented by a series of sine waves (resulting from fourier series or fourier transform). I also understand that light different colors of light correspond to different frequencies (what's the proof that these are frequencies of sine waves?). However say you were to measure the electric field magnitude of a light soure at an instant of time over a certain distance. What would the resulting function look like? Would it be a pure sinusoid? Would the function look different if the source were white light, or a laser source? Is there an easy experiment which you can do which would show this (or which has been done)? Or can someone provide me with a name of a textbook which shows this?