Final answer:
Humans can discriminate about 2 million colors due to the sensitive responses of three types of cones to different wavelengths of light, ranging from red (700 nm) to violet (425 nm). Not all animals see colors as we do; some see fewer colors, while others see similar ranges. The dispersion of white light explains the color sequence in a rainbow.
Step-by-step explanation:
The human ability to discriminate between thousands of different colors is a sophisticated sensory function that involves the eyes and brain working together. We perceive colors through light's wavelength and the responses of three types of cones in our eyes. These cones are sensitive to different ranges of light wavelengths, corresponding to red, green, and blue light.
The visual spectrum includes colors from red, at a wavelength of approximately 700 nm, to violet, at around 425 nm. Our eyes are capable of distinguishing roughly 500 levels of brightness, 200 different hues, and 20 steps of saturation, which amounts to about 2 million distinct colors. When our eyes receive light of pure wavelengths, we tend to see a limited range of colors, such as those seen in a rainbow. However, we perceive thousands of other hues through various combinations of wavelengths that our eyes detect and process.
Different animals have varying capacities for color perception. For example, dogs and cats may only see certain colors, such as blue, but not red and green. In contrast, apes and chimpanzees have color vision similar to humans. The phenomenon known as dispersion explains why a rainbow presents a sequence of colors based on wavelength. White light is a combination of all visible wavelengths, and its dispersion can demonstrate the full spectrum of colors that humans are capable of perceiving.