Final answer:
Colors dispersed by ice crystals in the atmosphere are arranged a) in a spectrum, following the order of colors based on their corresponding wavelengths.
Step-by-step explanation:
When colors are dispersed by ice crystals in the atmosphere, they are arranged a) in a spectrum.
This occurs because light is refracted differently for each wavelength as it passes through the ice crystals, similarly to the way light is dispersed by raindrops to create a rainbow. Dispersion leads to a spectrum, where the colors of white light are separated into the sequence of a rainbow, ranging from red to violet. Rather than being random or based on temperature, the dispersion and resulting color arrangement are strictly dependent on the property of light where each color corresponds to a different wavelength. This ordered spread of colors occurs whenever light changes direction due to wavelength-dependent processes, a phenomenon that happens in both rainbows and when light passes through a prism.