Wave Tutorial

Submitted by jshorb on Wed, 12/08/2010 - 20:48

The purpose of this Wave Tutorial is to help you learn about wave phenomena and how the properties of waves can be applied to things (such as electrons) that we would normally think of as particles. The videos show several representations of waves: a ripple tank (see below), a Wave Demonstrator; and a Slinky toy. Try to relate these representations to each other and figure out the common features they demonstrate about waves.

Try to describe how getting hit with a heavy ball is different than getting hit with a wave at the beach. They both can knock the wind out of you, they both could knock you over, and they both definitely have an impact. One, of course would deflect off of you and if it hit someone else, it would be less powerful. The other, however, could likely take down all of your friends standing behind you with just as much force - as if you were never standing in its way.

This is because the energyA system's capacity to do work. in a wave does not get carried within a specific entity. It's not a property of any given water moleculeA set of atoms joined by covalent bonds and having no net charge., it is moving through the body of water - this is what we call propagating.

Here, we look at a smaller version of that wave at the beach.

By shining light onto the ripple tank, we can see the waves being generated and propagating through the water. This traveling wave is generated by a vibrating rod. Just as the vibrating rod moves at a specific frequencyThe rate at which a periodic event occurs; specifically, the rate at which the waves of electromagnetic radiation pass a point. (ν), the waves move with the same frequency. Frequency can be described as the number of crests of a wave (or number of waves) passing through a given spot per second. For instance, waves crashing on a beach on a calm day would have a frequency of about 1-2 per second. The unitA particular measure of a physical quantity that is used to express the magnitude of the physical quantity; for example, the meter is the unit of the physical quantity, length. 'per second' is commonly called a Hertz (Hz).

In addition to moving at a given rate (frequency), waves also have a given spatial separation: the wavelengthThe distance between the crests of adjacent waves (or between any adjacent corresponding points in waves); used in the context of electromagnetic radiation. (λ), measured in meters. A wavelength is the distance between two nearest crests (or troughs). This distance is constant in the ripple tank shown: the shadows from the waves are equally separated. If we know how far apart the waves are (the wavelength) and also how quickly each one arrives (the frequency), then we know something about the distance traveled per second: the speed (v).

v=λ⋅ν