Polarisation
Transverse waves can be polarised. Normally transverse waves can oscillate in any angle on the plane perpendicular to the direction of travel - these are described as unpolarised waves. Polarisation means to create light which has oscillations in only one line perpendicular to the line of travel.
Waves can be described using a number of standard variables including: frequency, wavelength, amplitude? and period?. The amplitude? of a wave is the measure of the magnitude of the maximum disturbance in the medium during one wave cycle, and is measured in units depending on the type of wave. For examples, waves on a string have an amplitude expressed as a distance (meters), sound waves as pressure (pascals) and electromagnetic waves as the amplitude of the [electric field]? (volts/meter). The amplitude may be constant (in which case the wave is a c.w. or continuous wave) or may vary with time and/or position. The form of the variation of amplitude is called the envelope of the wave.
The period (T) is the time for one complete cycle for an oscillation of a wave. The frequency (F) is how many periods per unit time (for example one second) and is measured in hertz. These are related by:
When waves are expressed mathematically, the angular frequency (ω, radians/second) is often used; it is related to the frequency f by:
where A(z,t) is the amplitude envelope of the wave, k is the wave number and φ is the phase. The velocity v of this wave is given by:
where λ is the wavelength of the wave.
===The wave equation === In the most general sense, not all waves are sinusoidal. One example of a non-sinusoidal wave is a pulse that travels down a rope resting on the ground. In the most general case, any function of x, y, z, and t that is a non-trivial solution to the wave equation is a wave. The wave equation is a differential equation which describes a harmonic wave passing through a certain medium. The equation has different forms depending on how the wave is transmitted, and on what medium.
The Schrodinger wave equation describes the wave-like behaviour of particles in quantum mechanics. Solutions of this equation are [wave function]?s which can be used to describe the probability density of a particle.