Waves Study Guide

When a sound wave travels from one medium to another, such as from air into water, certain properties of the wave change while others remain constant. A key principle is that the frequency of the sound wave is solely determined by its source and does not change as it crosses a boundary between two different media. However, the speed at which sound propagates is dependent on the properties of the medium it is traveling through. Typically, sound travels faster in denser media (like water or solids) than in less dense media (like air). According to the wave equation, which states that velocity = frequency × wavelength, if the frequency remains constant and the velocity changes, then the wavelength must also change accordingly. Specifically, if the velocity increases, the wavelength will increase, and if the velocity decreases, the wavelength will decrease. This adjustment in wavelength ensures the consistent transmission of the wave's oscillations per second (frequency) across the boundary.

When a wave pulse is sent from a source, travels to a reflector, and returns, you can calculate the depth or distance to the reflector using the wave speed and the total time measured. The core formula is: depth (or distance to reflector) = (wave speed × round-trip time) / 2. This accounts for the wave traveling to the reflector and back (so, twice the actual one-way distance). This principle allows accurate measurement in applications such as sonar and seismic surveys, where knowing precise wave speeds and measuring round-trip times lets you deduce the depth or distance to a target or boundary.