Humans perceive different colors of visible light primarily by their wavelength. The visible spectrum of light ranges roughly from 380 nanometers (violet) to about 750 nanometers (red). Each color corresponds to a specific range of wavelengths: for example, blue light has shorter wavelengths, while red light has longer wavelengths.
While concepts like amplitude, energy, and frequency are related to light, wavelength is the primary attribute that determines the color we perceive.
- Amplitude refers to the brightness or intensity of the light, not its color.
- Energy is related to frequency and wavelength, but does not designate color directly.
- Frequency is inversely related to wavelength (higher frequency corresponds to shorter wavelength) and also does contribute to the perception of color, but the direct mechanism of color perception relies on wavelengths.
Thus, the correct answer is primarily: by their wavelength.