FIGURE 17.2 The physical properties of waves (a) Waves vary in wavelength (the distance between successive peaks). Frequency, the number of complete wavelengths that can pass a point in a given time, depends on the wavelength. The shorter the wavelength, the higher the frequency. Wavelength determines the perceived color of light. (b) Waves also vary in amplitude (the height from peak to trough). Wave amplitude influences the perceived brightness of colors.