What term describes the rate at which the disturbance travels through a medium?

• A. Velocity
• B. Frequency
• C. Wavelength
• D. Amplitude

Answer: (A)

The rate at which a disturbance travels through a medium is its velocity (the wave’s propagation speed). Velocity is how far the wave pattern moves per unit time, and for a given wave in a medium you can relate it with the equation v = f λ, where f is the frequency and λ is the wavelength.

Frequency tells you how often the disturbance repeats at a fixed point (cycles per second), not how fast the wave itself moves. Wavelength is the distance between identical points in successive cycles, which combined with frequency determines the speed but isn’t the rate of travel by itself. Amplitude is the maximum displacement of the medium, i.e., how big the disturbance is, not how fast it moves.

So velocity is the term that describes how quickly the disturbance propagates through the medium. For example, sound travels through air at about 343 m/s at room temperature; if the frequency is 440 Hz, the wavelength is roughly 0.78 m, and the wave’s velocity is the speed at which those crests move through the air.