Question

the electromagnetic spectrum
the ____________________ determines the color of visible light.
particles of the medium
wavelength (and frequency)
speed
amplitude

Explanation:

Visible light's color is determined by its wavelength (and frequency). Different wavelengths correspond to different colors in the visible spectrum. For example, shorter wavelengths like around 400 nm are violet, and longer wavelengths like around 700 nm are red. Since \(c = \lambda f\) (where \(c\) is the speed of light, \(\lambda\) is wavelength, and \(f\) is frequency), wavelength and frequency are inversely related for light (as \(c\) is constant in a vacuum). Amplitude affects the brightness (intensity) of light, not its color. The speed of light in a vacuum is constant (\(c = 3\times10^{8}\ m/s\)) and doesn't determine color. Particles of the medium (for light, which can travel in a vacuum, so no medium - dependent color determination from particles in the sense of this question) are not relevant here.

Answer:

wavelength (and frequency)