### Oscillations and Waves

An oscillator is a device that exhibits motion around an equilibrium point. In a pendulum clock, there is a change from potential energy to kinetic energy with each swing. At the top of the swing, potential energy is at maximum, and that energy is converted to kinetic energy as it falls and is driven back up the other side.

Now again at the top, kinetic energy has dropped to zero, and potential energy is high again, powering the return swing. The frequency of the swing is translated via gears to mark time. A pendulum will lose energy over time to friction if the clock isn't corrected by a spring.

Modern timepieces use the vibrations of quartz and electronic oscillators, rather than the movement of pendulums. An oscillating motion in a mechanical system is swinging side to side. It can be translated into a rotary motion turning around in a circle by a peg-and-slot. Rotary motion can be changed to oscillating motion by the same method. An oscillating system is an object that moves back and forth, repeatedly returning to its initial state after a period of time. At the equilibrium point, no net forces are acting on the object.

This is the point in the pendulum swing when it's in a vertical position. A constant force or a restoring force acts on the object to produce the oscillating motion.

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The motion of a simple harmonic oscillating system—when the restoring force is directly proportional to that of the displacement and acts in the direction opposite to that of displacement—can be described using sine and cosine functions. An example is a weight attached to a spring. When the weight is at rest, it's in equilibrium. If the weight is drawn down, there's a net restoring force on the mass potential energy.

When it's released, it gains momentum kinetic energy and keeps moving beyond the equilibrium point, gaining potential energy restoring force that will drive it in oscillating down again.

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6. Share Flipboard Email. Longitudinal Waves : The particle motion in this wave is parallel to the direction of energy transfer. It is key to note that the energy and particles move in the same direction. All sound waves are longitudinal waves. Standing Waves : Standing waves are formed when 2 waves travel towards each other eg.

The wavelength is the same and there is no net energy propagation. Standing waves have particles which remain stationary called nodes. The average speed of each particle is not the same at one cycle. The anti-node will be the fastest as it travels the farthest in one cycle. The distance between adjacent nodes or anti-nodes is half a wavelength. Microwaves are an example of standing wave. In a microwave, standing waves are established which is why a turntable is necessary.

## Sound Waves – Sound science for schools and colleges

Specifically, it is where the particles are most compressed in the wave. With displacement on the vertical axis, and time on the horizontal. The particle will move up and down in a sine curve type pattern. The highest point is called a crest. The lowest point is called a trough.

An example of a displacement vs time graph for a wave. This type of graph allows us to find both frequency which will be the number of crests in 1 sec and period which will be the time between crests. Note that the frequency and period have an inverse relationship. We can also find amplitude the maximum distance that the wave travels using this graph. This kind of graph tells us nothing about the wave speed or wavelength. A demonstration of how to find the period and amplitude on a distance vs time graph.

Displacement is on the vertical axis, and position or ie distance from an arbitrary origin in the material is on the x. The distance between peaks represents the wavelength. The wave speed can not be calculated directly from this graph, but can be found by combining the information from this and the displacement vs time graph as described in the next section. An example of a displacement vs position graph for a wave. This equation can be used to find the speed of a wave given it's wavelength and frequency. Deriving this is really rather obvious, but described below. Note, the frequency for a given wave is constant defined by the source thus, if the wave speed changes due to changing mediums then the wavelength also changes, but frequency remains constant.

There are different wavelengths that transverse waves travel at. The spectrum of different wavelengths have been divided into different sections. They are commonly given the following names in order of increasing frequency and decreasing wavelength. The amount of 'energy' in the waves decreases down the list, which is why X-rays are dangerous, and radio waves aren't. Visible light is split into colours from violet to red, violet having the highest frequency and red having the lowest. Electromagnetic waves are usually defined by their wavelength in a vacuum which seems rather silly, since frequency never changes, frequency and is what defines the characteristics i.

However weird it may sound, a Microwave oven at Earth does not emit the same wavelength of wave as one in space. There is a difference between the two locations, albeit a small difference. This is because light travels more slowly when it travels through a medium such as air; all electromagnetic radiation is slowed to some extent by the medium it is passing through.

That small difference may correspond to millions of light years in determining the distance of stars, so it is, in fact, very important to refer to vacuum values all the time just for setting a common ground for experiments.

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5. Vacuum is chosen as the common reference point because all electromagnetic radiation, no matter what the frequency, travels at the same speed in vacuum. As mentioned, the speed of light is slower when it's traveling through something, and higher-energy radiation is slowed down less. It is only in vacuum that it all travels at the same speed no matter what the frequency or energy is. During SHM, the pendulum swings from left to right and back the same way.

When the pendulum reaches it's highest point or highest amplitude, it is momentarily at rest and has zero kinetic energy. The kinetic energy it previously possessed when it was moving has been converted to potential energy at this high point. When he swings back down, the potential energy is changed back to kinetic energy and this is highest at the equilibrium point.

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## Physics equations/Oscillations, waves, and interference

At this point, though, there is zero potential energy. This model also follows the law of conservation of energy. On a pendulum, the period is independent of mass. Period on a pendulum only changes by the length of the string and the force of gravity. By shortening the string, the time decreases and the frequency increases.

Oscillation and Wave Speed - Exploring Wave Motion (2/5)

Longitudinal waves travel in one dimension, and so when they strike a boundary, they will be reflected back in the same direction, though the will experience a phase change i. This also applies to standing waves travelling in a stretched string. If both ends are connected to a boundary, then nodes points where the string doesn't move up and down will occur at both ends, and a number of antinodes will occur through the string, separated by nodes.

In an air column, it is possible to have both open and closed boundaries. At an open boundary, and antinode will occur, while at a closed one a node will occur. Whenever a wave is reflected from a boundary, the angle of reflection will equal the angle of incidence. Note that it is common for waves to travel in a full, or semicircle out from the source rather than in one line, which complicates reflection, because each wave is entering at a different angle.