Comparisons can also be made between the characteristics of the transmitted pulse and those of the reflected pulse. Once more there are several noteworthy characteristics. The goal of physics is to use physical models and ideas to explain the observations made of the physical world. First recall from Lesson 2 that the speed of a wave is dependent upon the properties of the medium. In this case, the transmitted and reflected pulse are traveling in two distinctly different media.
Waves always travel fastest in the least dense medium.
Thus, the reflected pulse will be traveling faster than the transmitted pulse. Second, particles in the more dense medium will be vibrating with the same frequency as particles in the less dense medium. Since the transmitted pulse was introduced into the more dense medium by the vibrations of particles in the less dense medium, they must be vibrating at the same frequency. So the reflected and transmitted pulses have the different speeds but the same frequency. Since the wavelength of a wave depends upon the frequency and the speed, the wave with the greatest speed must also have the greatest wavelength.