This question remind me of a doubt on the relation between colors and frequencies.
When we talk about a monochromatic color of a given frequency (or at least a narrow range of frequencies), it means only a generic plane wave with a narrow range of $k$:
$f(k(x – ct))$ where $\omega = kc$.
Or is this type of wave supposed to be sinusoidal as suggested by this answer?
Different musical instruments and the human voice can produce the same tune, (same frequency) but the sound is not the same. There is a difference of tone (I am not sure if that is the correct English word for the sound difference). That difference in tone is related to the wave shape in my understanding.
I wonder if it happens also with EM waves. Of course, man made radio waves can be very pure sinusoidal as mentioned here. But and about light?
Does the blue of a Yves Klein painting depends only on frequency or also on the wave shape?
Best Answer
If the wave is truly monochromatic then it will be sinusoidal. If it has a different profile then Fourier's theorem tells us that it can be built from an infinite series of (co)sine waves with increasing integer harmonics of the principle frequency (i.e. not monochromatic).