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Field emission and field electron emission are the terms. From wikipedia: The terminology is historical because related phenomena of surface photoeffect, thermionic emission (or Richardson–Dushman effect) and "cold electronic emission", i.e. the emission of electrons in strong static (or quasi-static) electric fields, were discovered and studied ...


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When it is saying the light rays converge, it means that they intersect. THe light rays intersect because the lens bends them so they all point at the same spot. I will explain more. When a point source emits light, it emits in all directions. This is why if you are in a dark room and you put a candle in front of a sheet of paper, you will see a diffuse ...


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Wavelength and wavenumber are redundant terms, as it sounds like you know. Their use is a matter of convention, which in my experience changes from field to field which you won't know until you've been around. So...if you know which one people use, go with the flow. Otherwise, use which one you know, and be confident; for questions of order-of-magnitude ...


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I don't think there's much to say beyond the obvious: You should use whatever terminology is most helpful in communicating the information that you want to communicate. That has to do with the audience you're talking to. Just like how you use °F when talking to Americans and °C when talking to non-Americans ... similarly it's often wise to use cm^-1 when ...


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Traditionally wavenumber is used in molecule spectrums such as infrared spectrums in organic chemistry where it is given in the incoherent SI-unit $\textrm{cm}^{-1}$. Mostly because one obtains convenient numbers on the axis. Also in most of the wave equations it is used, because again you can make the convenient substitution $k \equiv \frac{2\pi}{\lambda} = ...


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As an alternative to Anna's nice historical discourse a heuristic that covers modern uses of the phrase would be that energies are "high" when the QCD can be treated as perturbative. That regime sets in considerably above the nucleon mass scale, say 10s of GeV. So LHC physics is in, JLAB physics is out (even with the 12 GeV upgrade).


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Elementary particle physics is an outgrowth of what was high energy physics, historically at the time. X-rays were high energy physics when first discovered, they are part of the tools of solid state physics now. Alpha particles and gamma rays were high energy physics at their time, they are nuclear physics now. Mesons discovered in cosmic rays started ...


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This is a relatively natural use of language, and people do use it a lot. There is no such thing as true zero temperature in a physical system (partly because of the third law of thermodynamics, and partly because $T=0$ statistical mechanics only makes sense as a $T\to 0$ limit), so when you talk about zero temperature you are really using the limits $T\to ...


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Definition of finite is a bound and non-zero number.


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The terminology "continuous variable system" is non-standard, but likely refers to the fact that any canonical quantization of a classical Hamiltonian system (i.e. a system described by a continuous phase space) must have an infinite-dimensional Hilbert space since the canonical commutation relation $$ [x,p] = \mathrm{i}\mathbf{1}$$ cannot be realized on ...


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A current-current diagram is a diagram in the diagrammatic expansion of a current-current amplitude. For the latter, see. e.g., equation (1.1) in Keith Hamilton, The Standard Model Part II: Charged Current weak interactions I, http://www.hep.ucl.ac.uk/~campanel/Post_Grads/2013-2014/SM-CC-Weak-Interactions-I.pdf


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You're correct. The speed is only the magnitude of the velocity. However, since the speed doesn't change it cannot change direction, as that would require acceleration. Of course, that assumes the speed is only in one dimension, because it could plot the speed of something with a circular motion, or any other motion for that matter. A spaceship in a circular ...


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The simple answer is that displacement, in this context, is distance. There are other uses, such as the weight of a ship, but that is not germane. Consider that the area under the line is x times y. In this case the x axis has the units of seconds, and the y axis has the units of meters per second. So when multiplying them out, $$sec\times\frac{meters}{sec} ...


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The graph shows a constant speed, which is positive, so we know that the velocity is not changing sign. Depending on the context of the graph (is it dealing with 1D motion or curvilinear motion) we could tell a lot. Technically, on a traditional velocity vs time graph, one is plotting a component of velocity, complete with signs. I don't think the plot is ...


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The amount of work done by unit charge between any two nodes of current carrying circuit is called the potential difference between those nodes. The amount of work done against the electric field by displacing (without acceleration) a unit test charge from one terminal to other terminal in an open circuit is called the electromotive force. Obviously when ...


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There are a lot of complex answers. I am just gonna give you a simple one. When we talk about Inertia, just think of it as a property of a body that allows it to stay in its state of rest or uniform motion. Just think of it as a resistance to change in the state of body. Just for a simple example, say you have a pitcher of water, if you put your finger in ...


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With the term "inertia" it is understood the capability of a body of opposing resistence to changes of its status of motion, caused by some forces. Remember that, in general, the motion of a mechanical system can be decomposed in center of mass (CoM) motion and a rotating motion about the CoM. Indeed, one usually speaks about the inertial mass for the first ...


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As others have said, escape velocity is a speed, not a velocity. As to why, see the etymology of the word velocity: early 15c., from Latin velocitatem (nominative velocitas) "swiftness, speed," from velox (genitive velocis) "swift, speedy, rapid, quick," of uncertain origin. Velocity used to mean speed, and we still say things like "high velocity ...


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Yes, escape velocity should really be escape speed. The Wikipedia article on escape velocity states this explicitly. I doubt there is any logical reason for using the term escape velocity and I suspect it is an accident of history. You might want to ask on the History of Science SE how the term originated - a quick Google failed to retrieve any information ...


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The term "preliminary" does not refer to the runs. It refers to the status of results and figures that have not been properly reviewed and/or approved for publication yet.


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Inertia is the resistance of movement when a body is a subject for some sort of stress. In Newtonian physics, we can define inertia according to Newton's Second Law of Motion $\mathbf{F}=\dfrac{d\mathbf{p}}{dt}\simeq \dfrac{\Delta \mathbf{p}}{\Delta t} = m \dfrac{\Delta \mathbf{v}}{\Delta t} = m\mathbf{a}$. In this case, $m$ is the inertial mass and the mass ...


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In classical mechanics, inertia=force applied/acceleration applied. It's how much acceleration you apply to a body for the amount of force you apply. You could also phrase it as how much resistance a body has to change in velocity.


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Inertia is not a force. There are four fundamental forces: (1) Strong nuclear force carried by gluons, (2) Electro-magnetic force, (3) Weak force carried by intermediate vector bosons, and (4) Gravity. In addition to the four fundamental forces, the word "force" is used to describe these mechanical operations: (1) Applied force actively exerted, (2) Normal ...


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Inertia is considered in physics when we want to do work in sense of physics. It's not a force exerted by body instead it is force need by body to move. If it was a force exerted by body then equation will itself be changed. In equation acceleration is the need one to move it. If it was exerted by body then mass and acceleration would not be mentioned it ...


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There can be two answers. The first one, concerns Newton's third law. For me to extert a force upon a body and change its state of motion, the body needs to exert a force equal in magnitude and opposite in direction to me. Or, in other words, the body excerts a resistance to me. This action and reaction forces are used all the time when you consider systems ...


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It isn't necessary to introduce the effective potential in orbital mechanics but it is really useful. Let's say we have a particle moving in a central gravitational potential. Newton's laws give you a vector equation of motion \begin{equation} m \ddot{\vec{x}} = - \nabla U \end{equation} where $U = - G M m /r$. In a general coordinate system this is a ...


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I agree with your definition of locality (probably not surprising :)). Causality I would say is the statement that an event in the future should not affect an event in the past. We can formulate this in classical physics terms. Causality is necessary in order for there to be a well defined initial value problem: I should be able to choose an initial time ...


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i only know the effective potential when talking about central forces situations in classical mechanics, there it is defined as: $V'(r) = V(r) + \frac{L^2}{2mr^2}$ with V(r) being the radial potential, the second term can be considered a centrifugal potential which results from considering the azimuthal part of the kinetic energy. $E = V + E_{kinetic} = ...


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Causality means that if something happens before in one reference frame of your choice, it happens before in any other existing reference frame in the universe. Locality means that if two events are space-like separated then it exists at least one reference frame where they happen at the same time; if two events are time-like separated, then it exists at ...


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As you've seen, the word quadrature is overladen with many, none-too-precise meanings. Here the "quadratures" loosely refer to the position and momentum observables: $$\hat{x} = \frac{1}{\sqrt{2}}(a + a^\dagger)$$ $$\hat{p} = \frac{i}{\sqrt{2}}\,(a - a^\dagger)$$ where $a,\,a^\dagger$ are the lowering/ raising operators and I've normalized the two ...


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A representation of the Lorentz group implies a set of matrices $(S_{\mu\nu})_a{}^b$ (one for each $\mu,\nu$) that satisfy the Lorentz algebra, i.e. satisfies a relation of the form (I am not keeping track of signs) $$ [S_{\mu\nu} , S_{\rho\sigma} ] = i ( \eta_{\mu\rho} S_{\nu\sigma} + \cdots ) $$ What this means is that there is a vector space, with vectors ...


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Notation: I will write a Poincaré transformation as ${x'}^\mu = {\Lambda^\mu}_\nu x^\nu + a^\mu$, the operator representing this transformation on the Hilbert space is $U(\Lambda, a)$. An infinitesimal transformation with ${\Lambda^\mu}_\nu = \delta^\mu_\nu + {\omega^\mu}_\nu$ and $a^\mu = \epsilon^\mu$ can be expanded as $$ U(\delta + \omega, \epsilon) = 1 ...


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I know this is an old thread, but I had to figure this out for a problem on my physics homework. What helped me to understand this is to think about 2 objects on a spinning disk, one being close to the center of the disk and one being close to the outside of the disk. Angular (rotation) speed deals strictly with the angle. How long does each object take to ...



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