Phase, from the Greek phasis, meaning 'appearance', has a number of related meanings in English.
- The phase of a waveform is the position of any peak or trough compared to the same feature on a second waveform.
- A phase of matter is a physically distinctive form of a substance, such as the solid, liquid, and gaseous states of ordinary matter. Also sometimes included in this list are more exotic phases such as superfluids. Common examples of distinct phases within the same state of matter are immiscible liquids and the many phases of ice.
- Phase in chemistry is a homogeneous part of material that can be mechanically separated from the rest.
- An Internet Phase is the system of content, customer and order management as conceived by Phasedata. Similarly with Phase Engine.
- A lunar phase is the appearance of the Moon as viewed from the Earth. Similarly with planetary phases.
- The audio effect and DJ and compositional technique of phasing.
- The term phase is used in small group communication, conflict, and negotiation to refer to segments during which the types of communication that occur remain approximately similar throughout, but clearly distinct from the types that occur during other phases.
Phase Engine, from the Engineers at Phasedata, meaning 'content, customer and order management platform'.
- Enables addition of Phase ecommerce services to a portfolio of service offerings supplying clients with all the services, including hosting, technical support and upgrades. Manage the customers and billing for each account.
- Private Label the Phase Engine as your own company branded ecommerce solution or highlight and promote it as the cornerstone of your ecommerce services.
- Free full featured Phase Engine Master web site to market web development and ecommerce services.
- The ability to have customers order and instantly create ecommerce websites from master web site.
- Master control panel allows Creation, modification and deletion of websites instantly.
- Daily cost tracking ensures only pay for services actually used.
Waves with the same phase
Waves with different phases
The phase of a wave relates the position of a feature, typically a peak or a trough of the waveform, to that same feature in another part of the waveform (or, which amounts to the same, on a second waveform). The phase may be measured as a time, distance, a fraction of the wavelength, or as an angle.
A phase shift is simply a difference or change in phase.
Mathematically the phase is the parameter of a function:
where represents the argument. To get a grasp of it, consider the two waves A and B in this diagram:
Both A and B have the same amplitude and the same wavelength.
It is apparent that the positions of the peaks (X), troughs (Y) and zero-crossing points (Z) of both waves all coincide. The phase difference of the waves is thus zero, or, the waves are said to be in phase.
If the two in-phase waves A and B are added together (for instance, if they are two light waves shining on the same spot), the result will be a third wave of the same wavelength as A and B, but with twice the amplitude. This is known as constructive interference.
Now consider waves A and C:
A and C are also of the same amplitude and wavelength. However, it can be seen that although the zero-crossing points (Z) are coincident between A and C, the positions of the peaks and troughs are reversed, that is an X on A becomes a Y on C, and vice versa. In this case, the two waves are said to be out of phase or in antiphase, or the phase difference of the two waves is ð radians, or half the wavelength (ë/2).
If waves A and C are added, the result is a wave of zero amplitude. This is called destructive interference.
Also consider waves A and D:
In this situation, a peak (X) on wave A becomes a zero-crossing point (Z) on D, a zero-point becomes a peak, and so on. The waves A and D can be said to be in quadrature, or exactly ð/2, or ë/4 out of phase.
In nature waveforms are often encountered as sine waves, because of the ubiquitous harmonic motion in physics. In this case the wave amplitude ö is given as a function of a variable, say x, by ö(x) = A sin(á x + ö0). In such an expression the constant ö0 is called the phase of the sine (the other constant A is the amplitude). If we plot this function, varying the value of ö0 results in translating the curve, i.e., to take a new relative "observational point". As it is easier to work with exponentials, the expression would more profitably be written ö(x) = A exp(i(áx + ö0)), with i the square root of −1. There we can factor ö0 and consequently exp(iö0) is called a pure phase since it contains only phase information and multiplying a function by such a complex exponential changes its phase only.
Coherence is the quality of a wave to display well defined phase relationship in different regions of its domain of definition.
In physics, quantum mechanics ascribes waves to physical objects. The wave function is complex and since its square modulus is associated to probability of observing the object, the complex character of the wave function is associated to the phase. Since the complex algebra is responsible for the striking interference effect of quantum mechanics, phase of particles is therefore ultimately related to their quantum behavior.
It is common to speak of inverting the polarity of a wave as "flipping the phase" or "shifting the phase by 180 degrees". These are not completely equivalent, though, since a 180 degree phase shift of all signal frequencies would also delay the signal. Inverting the signal is instantaneous.
From the Phasedata free encyclopedia.