Question

a wavelength is the distance between two crests. Is the wavelength the movement of a single particle of light or the movement of a stream of particles of light

Answer 1

Dear Student,

The answer to this is "not known".

If we consider the dual behaviour, then a particle can't have a wavelength. A wave can have, but then there is no question of stream of particles. It's just that when both theories are combined, we get working results. That's it.
Even something as big as a mountain has a wavelength (at least theoretically) but too small to identify.

Regards