Final answer:
When the frequency of a wave decreases, the wavelength increases due to their inverse relationship, provided that the wave's velocity remains constant.
Step-by-step explanation:
When the frequency of a wave decreases, the wavelength of the wave increases. This is due to the inverse relationship between frequency and wavelength. If you consider the wave equation, which is velocity (v) equals frequency (f) multiplied by wavelength (λ), and if the velocity of the wave remains constant, a decrease in frequency must result in an increase in wavelength. This is visually evident if you picture waves passing a stationary point: fewer waves (lower frequency) will pass by in a given amount of time, which means those waves must be more spread out (longer wavelength).