Waves

About Waves

Put in the simplest terms, a wave is something that wiggles in space and time. Waves extend from one place to another. The can vibrate periodically (like the sound of a violin note) or non-periodically (for example, the sound of an explosion.) All waves have the following properties:

The strength of the vibration is the amplitude.
How often the vibration occurs is the frequency.
The distance the wave has traveled between maximums is the wavelength.
Since a given wave propagates at a set velocity through a material, if you increase the wave's frequency, the distance between crests drops (a decrease in wavelength). Mathematically, wave speed = frequency x wavelength , so for a constant wave speed, frequency and wavelength are inversely related.
One of the most interesting property of waves is that when two waves pass through each other, their effects are added together. This is called interference.

There are many more wave properties we can't get into for lack of space.

Wave properties are key to understanding particle behavior.

Imagine a light source being blocked by a sheet of metal with two slits in it. A few meters away there is a screen. For a given point along the screen, there are two light waves hitting the screen (one through each hole). These two light waves travel different distances to reach the screen, so they interfere with each other, creating an interference pattern.

It turns out that if you repeat the same experiment using a particle beam instead of a light source, you record a similar interference pattern. This means that all particles have wave properties. For example, here's a real interference pattern caused by an electrons scattering off gold foil:

It is a very strange concept that what we think of as solid matter particles are, in reality, wave-like because matter particles have frequency, wavelength, and can interfere with each other. It is important to note that sub-atomic particles' wavelengths are not due to the particles "jiggling" around; rather, the particles' properties phase in and out. For example, a light particle (the photon) is a wave because its electromagnetic field phases from one sign to the other.

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