This sound wave is generated by a speaker broadcasting a single frequency, so the speaker cone is oscillating back and forth in simple harmonic motion. ![]() From heavy to light, the reflection is as if the end is free.Īnything that vibrates is producing sound sound is simply a longitudinal wave passing through a medium via the vibration of particles in the medium.Ĭonsider a sound wave traveling in air. For a pulse going from a light rope to a heavy rope, the reflection occurs as if the end is fixed. If the pulse is traveling along one rope tied to another rope, of different density, some of the energy is transmitted into the second rope and some comes back. If the end is free, the pulse comes back the same way it went out (so no phase change). If the end is fixed, the pulse will be reflected upside down (also known as a 180° phase shift). The wave will be reflected back along the rope. Consider what happens when a pulse reaches the end of its rope, so to speak. This applies to both pulses and periodic waves, although it's easier to see for pulses. For a transverse wave on a rope or stretched spring, the wave speed is determined by the tension (F) and the mass per unit length:įor a sound wave, the speed is determined by either Young's modulus or the bulk modulus (discussed in chapter 10) and the density: The wave speed is essentially the speed at which the neighboring particle responds to this force that response time is determined by the mass of the particle and the size of the force exerted. For a wave to propagate, each disturbed particle must exert a force on its neighbor. The speed of a wave traveling through a medium depends on properties of the medium. The maximum speed of a particle is determined by the wave amplitude and frequency. In a uniform medium, the wave travels at constant speed each particle, however, has a speed that is constantly changing. As the wave travels through the medium, the particles of the medium oscillate in response to the wave. There is a big difference between what the wave does and what the particles in the medium do. The wavelength can then be found from the equation above.Ī sine wave oscillation is also followed by each particle in the medium, as the following diagram shows: Note that the frequency of the wave is set by whatever is producing the disturbance, while the speed is determined by the properties of the medium. ![]() Speed - this is given by v = frequency x wavelength The particles on the surface of the water travel in circular paths as a wave moves across the surface.Ī periodic wave generally follows a sine wave pattern, as shown in the diagram.Ī number of parameters can be defined to describe a periodic wave:Īmplitude - the maximum distance a particle gets from its undisturbed positionįrequency (f = 1/T) - number of cycles in a certain time, usually in 1 second. ![]() Surface waves, such as water waves, are generally a combination of a transverse and a longitudinal wave. In a longitudinal wave, such as a sound wave, the particles oscillate along the direction of motion of the wave. In a transverse wave, the motion of the particles of the medium is at right angles (i.e., transverse) to the direction the wave moves. ![]() Waves can also be separated into transverse and longitudinal waves. There is a close connection between simple harmonic motion and periodic waves in most periodic waves, the particles in the medium experience simple harmonic motion. A pulse is a single disturbance while a periodic wave is a continually oscillating motion. Waves can be broadly separated into pulses and periodic waves. Light, and other electromagnetic waves, do not require a medium we'll deal with those next semester. For now, we'll focus on mechanical waves, requiring a medium in which to travel. We'll shift gears again, moving on to waves.Ī wave is a disturbance that transfers energy from one place to another without requiring any net flow of mass.
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