What is Phase: Definition and 1000 Discussions

In the physical sciences, a phase is a region of space (a thermodynamic system), throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, magnetization and chemical composition. A simple description is that a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water. The glass of the jar is another separate phase. (See state of matter § Glass)
The term phase is sometimes used as a synonym for state of matter, but there can be several immiscible phases of the same state of matter. Also, the term phase is sometimes used to refer to a set of equilibrium states demarcated in terms of state variables such as pressure and temperature by a phase boundary on a phase diagram. Because phase boundaries relate to changes in the organization of matter, such as a change from liquid to solid or a more subtle change from one crystal structure to another, this latter usage is similar to the use of "phase" as a synonym for state of matter. However, the state of matter and phase diagram usages are not commensurate with the formal definition given above and the intended meaning must be determined in part from the context in which the term is used.

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1. Phase difference between two light waves of the same frequency

the diagram. i found that the phase difference between them is 100º but how is the answer 260 can someone please explain?
2. Relationship between Fourier coefficients and power spectral density

Here, ##\Phi(f_{x_n},f_{y_m})=|\mathscr{F(\phi(x,y))}|^2 ## is the Power Spectral Density of ##\phi(x,y)## and ##\mathscr{F}## is the Fourier transform operator. Parseval's Theorem relates the phase ##\phi(x,y)## to the power spectral density ##\Phi(f_{x_n},f_{y_m})## by...
3. A Relativistically invariant 2-body phase space integral

I encounter a function that I don‘t know in the calculation of Relativistically invariant 2-body phase space integral: in this equation, ##s##is the square of total energy of the system in the center-of-mass frame(I think) I don't know what the function ##\lambda^{\frac{1}{2}}## is. There are...
4. Phase currents of Trapezoidal switching

For trapezoidal switching or 180 degree switching these are the waveforms when i referred to the website 180 switching when i calculated the RMS value of the phase voltage it is Vp = 0.4714Vs so assuming the Vs = supply voltage = 20V and each phase - phase resistance as per the data sheet is...
5. I Hidden phase in polarization tests of Bell's inequality?

Hi there, i must preface with saying my understanding of the problem is limited to undergraduate quantum mechanics, since my spacialization is chemistry. I know the basic principles, like hilbert spaces, vector bases etc... I'm only asking this question because i genuinely want to understand...
6. I Topological phase transitions for the whole Universe...?

Physicist Grigory Volovik has put forward some ideas about the universe undergoing a topological phase transition (especially in the early stages of the universe). He published a book called "*The Universe in a Helium Droplet*" where he explained his ideas. You can find a brief discussion here...
7. I Two Waves In Phase: Exploring the Possibility w/ Graphs

May I know how is it possible for two waves to be in phase when they have different amplitude? I couldn't find any existing graphs that clearly shows how the two waves are in phase, would anyone be able to sketch it out so I can have a look. Thank you:smile:
8. Three Phase Per Unit System - Mark up, represent as single phase equiv

I'm seeking some reassurance I've understood the question since there are no answers given in the book and I'm getting a bit tied up in knots. What I am struggling with most is there are three per unit values for impedance already noted on the diagram without qualifying what ##Z{base}## is or...
9. I Phase Contrast Telescope - Part II

Over a year ago I started a post on a theoretical proposal for a phase contrast telescope (link here https://www.physicsforums.com/threads/why-no-phase-contrast-telescopes.1010127 ). However, the post was based on real experiences that were so different from anything I’ve ever experienced in my...
10. Rearrange formula and work out phase angle

so far i think Ip = 10 f = 1000hz struggling with the phase angle
11. I Does an electron have a quantum phase frequency?

Stationary solutions to the Schrödinger equation factor into a spatial part, e.g. atomic and molecular orbitals, and a temporal part that gives the phase rotation frequency. It is often assumed that adding a constant to the potential leaves the physics unchanged. And clearly, any "spectroscopic"...

34. I EM wave propagation: respective phase of E and M field

Hi alltogether, I have been confused about a certain topic of EM wave propagation: it´s clear to me that E and M field are perpendicular to each other (I know Maxwell´s equations well). But: sometimes you can find on the internet that both fields are in phase...
35. Measuring Phase to Phase voltage using Multimeter

I want to understand the concept of measuring the phase to phase voltage using multi meter. For example if i want to measure R-Y voltage, i connect the positive probe of the multi meter to the R phase and the negative probe to the Y phase. But both phases will be sinusoidal, so how does it...
36. I Phase velocity and frequency of a matter wave

The relationships for matter waves are (see e.g. https://en.wikipedia.org/wiki/Matter_wave): λ = h / p and E = h f, where E = m c2 From this the phase velocity can be derived and we get vph = c2 / v. v is the group velocity, which is also the velocity of the particle. If I consider these...
37. Finding equilibrium temperature when there are phase changes

If there weren't phase changes occurring I know that the temperature equilibrium would be ##T_e=\frac{m_{ice}c_{ice}T_{ice}+m_{w}c_{w}T_{w}}{m_{ice}c_{ice}+m_{w}c_{w}}##. Now, by repeating the reasoning to get the above formula (##\sum \Delta Q=0##) and adding the phase changes of the water...
38. Engineering Half-power cut-off frequency and frequency and phase response.

I have been given the attached following question: FIGURE 2 shows the response of a first-order filter to a step input. Estimate the half-power cut-off frequency of the filter and sketch its frequency and phase response. I believe that I have correctly calculated the half-power cut-off...
39. Incorrect Calculation of Time for Reactor Energy Phase Change

I tried using the equation Q'*t= Q1+Q2. Where Q' is the energy of the reactor aka 200,000 kJ and t is the time. Take Q1 to be (1/2m*2257) and Q2 to be (1/2m*4.184*90). The 90 is the change in temperature for the phase change to occur from liquid water to gas, or boiling. Plugged everything in...
40. A How Does Quantum Theory Provide a Measure for Microstates in Phase Space?

*Pathria, Statistical mechanics*"The microstate of a given classical system, at any time, may be defined by specifying the instantaneous positions and momenta of all the particles constituting the system. Thus. If ##N## is the number of particles in the system, the definition of a microstate...
41. The magnetic phase change of an electromagnetic wave during reflection

If the question had mentioned ##\overrightarrow{E}## instead of ##E_\bot##, then we could have used ##\overrightarrow{B}=\dfrac{1}{v}\widehat{k}\times \overrightarrow{E}## to get the direction of the magnetic field. But the question had only mentioned ##E_\bot##. To my understanding, knowing...
42. A Local phase invariance of complex scalar field in curved spacetime

I am stuck deriving the gauge field produced in curved spacetime for a complex scalar field. If the underlying spacetime changes, I would assume it would change the normal Lagrangian and the gauge field in the same way, so at first guess I would say the gauge field remains unchanged. If there...
43. Extraction Flash Calculation - 4 Component and 2 Phase System

I am performing extraction flash calculations for 4 component and 2 phase system. For anyone somewhat shaky with what extraction flash calculation is; extraction is performed, feed composition is known and we are calculating compositions of both phases at equilibrium, mole fraction of every...
44. What's the best shape function/element in finite element methods for phase field simulation?

What's the best shape function/element in finite element methods for phase field simulation?
45. Modelling of two phase flow in packed bed (continued)

Previous post linked here, where a model for the two phase flow of air through a packed bed was developed: https://www.physicsforums.com/threads/modelling-of-two-phase-flow-in-packed-bed-using-conservation-equations.1008754/ The first few comments on this new thread will be copies of the...
46. Convert 1 phase to 3 phase by using an old washing machine

We were in the process of going off grid when a tree fell over our power line. Hence we got off grid before we were ready as we didn't want to repair the power line. Now everything in the house runs on solar power, except for the well pump. The problem with the well pump is that it is a 3 phase...
47. Engineering Decomposition minimal phase & all pass

Hey everybody! I have put G1 = (1-s)/(2-10s) & G2 = (2-10s)/ (2 +10s) but than I read that all poles and zeroes should be inside the unit circle, and I don't know how to move the Zero S_01 = 1 to the unit circle
48. A How is phase velocity related to deflection angle?

Refractive index is a function of velocity in the medium. How is this related to deviation angle inside the medium? I am not asking for the known formula, but for the mechanism behind it.
49. How to wire a house using 3 phase

We are getting 3 phase power delivered to our property via our own dedicated transformer. We want to rewire the house and other buildings so that we can use different appliances on different phases. We have 4 air conditioners, 3 hot water units and the usual assortment of things you would find...

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