"White" light rays

[Roger Breton]

I was asked: how are the waves arranged, spatially, in a white beam? When
that beam is dispersed with a prism or grating the individual component
light rays present in that beam are spread out spatially according to their
wavelength / refractive index / frequency. But the question is how are the
individual component light rays arranged spatially in the first place in the
original white: are they sandwiched together, overlapping each other,
serially arranged, randowmly distributed around the axis of propagation?

Roger Breton

 

[Don Stauffer]

All mixed together, generally, though the exact source of the light can
have some effect. If it is a radiating black body, all frequency/color
photons are mixed together throughout the wavefront. If the beam passes
through an aperture that causes diffraction, the diffraction wings will
have some variation in distribution with color.

 

[Pieter Kuiper]

I was asked: how are the waves arranged, spatially, in a white beam? When
that beam is dispersed with a prism or grating the individual component
light rays present in that beam are spread out spatially according to their
wavelength / refractive index / frequency. But the question is how are the
individual component light rays arranged spatially in the first place in the
original white: are they sandwiched together, overlapping each other,
serially arranged, randowmly distributed around the axis of propagation?

There is only one electric field in the beam. It varies as a function of
time as the sum of the sine function of the different frequencies.

It is very similar to sound waves: your eardrum vibrates as a function
of times as the sum of any sine waves, and the ear sorts this out as a
kind of Fourier analyzer.