A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochromatic light refers to electromagnetic radiation that contains a narrow band of wavelengths, which is a distinct concept.
Does a beam of electrons become more monochromatic as it propagates?
Can you cool an electron beam noticeably?
I'm considering a very narrow beam of electrons with, for example an initial width in the order of 100 nm, and an energy around 1 keV and with a very small divergence angle (maybe 0.01...