Final answer:
The psychological effect of the length of light waves is referred to as color, with hues corresponding to different wavelengths in the visible spectrum. The term hue directly relates to wavelength, and saturation refers to the intensity or brightness of colors.
Step-by-step explanation:
The term that refers to the psychological effect of the length of light waves is color. The visible spectrum of light consists of various wavelengths, each perceived as various colors by the human eye. Wavelengths at the red end of the spectrum are longer, and we perceive them as red, while wavelengths at the blue/violet end are shorter and correspond to our perception of those colors.
The mnemonic ROYGBIV (red, orange, yellow, green, blue, indigo, violet) helps us remember the order of colors based on their increasing wavelength. It is important to note that while hue directly relates to wavelength, saturation refers to the intensity or brightness of a color, with higher saturation representing more vivid colors.