Final answer:
The wavelength of sound changes when it passes from one medium to another with a different propagation speed, while the frequency remains constant. This is due to the relationship v = fλ, where the speed of sound is different in different media.
Step-by-step explanation:
When sound passes from one medium to another, where its propagation speed is different, the frequency of the sound remains constant because it is dependent on the source of the sound. However, wavelength changes because the speed of sound is different in the two media. The relationship between speed (v), frequency (f), and wavelength (λ) is given by the equation v = fλ. If the speed of sound increases, but the frequency remains the same, then the wavelength must also increase; conversely, if the speed of sound decreases, the wavelength decreases.
Example of Wavelength Change
Consider the sound being produced by a speaker in the air and traveling into water: the sound maintains the same frequency as it moves from air to water, but since sound travels faster in water than in air, the wavelength of the sound increases.