Barrier Definition and 241 Threads

Hi all, I came across this figure in a textbook. Simple stuff, but can get tricky: I don't understand why the sign convention flips upon entering the barrier (region II), but I guess the book is correct and that I should just take it as a fact. If anybody has a reasonable thought to add...

I can not find what is exactly Peierls-Nabarro barrier? Could you gave me some explanation or reference. Everything I found are just different papers which I can not understand.

The venturi effect of the new ARX bullet almost doubles side exit velocity. What happens if the exit velocity exceeds the sound barrier in a fluid like a gelatin block?

Is there a way to measure the amount of voltage used when transmitting from the blood brain barrier to a particular muscle outside of the skin or is the dermis too thick?

I have a problem of a vehicle that impacts a barrier and knocks it over. At what minimum velocity does the barrier tip? (assuming it did not slide and there is no damage absorbing energy in the collision), sort like Barrier 2 ft wide, 2 ft tall, 6 ft long, 3600 lbs. Vehicle 2000 lbs, bumper...

If a field line is moved into a superconductor it meets resistance. This resistance is modeled by adding an image flux thread outside the superconductor which then attracts the flux thread being moved into the superconductor. Why is this attractive force an accurate model of the resistance a...

Homework Statement Consider a square hill barrier produced by a 10V potential. Incident upon this barrier is a steady stream of 5eV electrons. (a) If half the electrons are transmitted, how thick is the barrier? (Please derive the transmission probability rather than merely quoting it.)...

Suppose I have a region from 0 to L. I have a barrier potential V from x1 to x2, such that 0<x1<x2<L. The potential is 0 everywhere. I have obtained the wave-function by considering the propagation from left to right. Now if I consider the propagation from right to left should I get a different...

Homework Statement Picture of Problem: Homework Equations $$\psi(x) = A_n e^{ikx} + B_n e^{-ikx}$$ for n=1,2,3 The Attempt at a Solution I know i need to relate the wave functions $$A_n e^{ikx} + B_n e^{-ikx}$$ for n=1,2,3 (the three areas of the barrier - before barrier, inside barrier...

Hello everyone, First up, I know nothing about physics or chemistry. That out of the way, let's begin. I recently read about a very interesting material called Starlite which is supposedly a remarkable thermal barrier but is presumed lost to the world because the inventor kept the formula...

Hi, For a PN junction diode, am I correct in thinking that the barrier potential (due to depletion region and hole-electron recombination etc.) is the same as the 'forward voltage' quoted on datasheets? Also, when a forward bias condition is created and the applied voltage is greater than the...

It is known that the penetration depth of photon into a material depends on the energy of the photon, density and atomic number of the material; because the photon energy is normally smaller than the potential against the penetration of photon, which is the potential barrier, so the incident...

Reposting from another section... Can anyone explain to me how an excimer is formed? Like structure wise? Considering Xenon. I've gathered that an excited state Xe*, ground state Xe, and a 3rd body M react resulting in an Xe* excimer + M(carrying away excess energy). I'm struggling to find...

Homework Statement I am trying to calculate the transmission and reflection coefficients for rectangular finite potential barrier between (-a, a) for a particle of mass m with energy equal to the height of the barrier (E = V0 > 0). Homework Equations...

As we know that in a metal-semiconductor junction schottky barrier arise. My question is that this is generally represented as sudden discontinuous jump in energies of conduction band on either side. But this will mean that the electric field at that point is infinite since electric field is...

Barrier tunneling happens when, let say, an electron tunnels through a region when it has lower energy compared to the energy of the region (potential barrier). What differs Quantum from classical mechanics is that CM states the electron will never be able to penetrate the potential barrier...

Homework Statement Prove (6-44) which expresses the reflection and transmission coefficients in terms of the ratio E/V0.Homework Equations [/B] The Attempt at a Solution express k1 and k2 in terms of V/E? [/B]

Homework Statement A car, assumed to be rigid and having a mass of 800 kg, strikes a barrel-barrier installation without the driver applying the brakes. From experiments the magnitude of the force of resistance F_r, created by deforming the barrels successive, is shown as a function of the...

Homework Statement The windmill is 400 feet tall and each of it's three blades are 130 feet long. At how many rpms will a blade tip break the sound barrier? Speed of sound: 1125ft/sec Homework Equations Linear speed: v = rω Angular speed: ω = Θ/Time The Attempt at a Solution...

I have been chewing up some time ago the Schottky-Mott theory of Schottky Barrier height (which ignores the surface states). All the deduction seems to ground on fundamental thermodynamical principles (as the equality of Fermi levels- i.e. equality of chemical potential in equilibrium) but there...

The equation for the barrier potential is as follows: Vb = Vt loge(Na*Nd/square(n)) mV where Vt=KT/e This equation shows that the barrier potential is directly proportional to the temperature. So as temperature increases the barrier potential should increase. But in contradiction to...

Homework Statement Background: The problem is to find the uncertainty relationship for the wave equation for a delta function potential barrier where ##V(x)=\alpha\delta(x)##. Check the uncertainty principle for the wave function in Equation 2.129 Hint: Calculating ##\left< p^2 \right> ##...

I have some questions about double slit experiment. 1) Sometimes photons or electrons should bounce off the initial barrier and nothing should be detected in the plate. ¿Is this correct? i find a video saying that NOTHING is detected in the barrier, only in the plate. 2) If we put 1...

Hi all, How I can calculate the Potential Barrier when we have a metal- semiconductor, metal- metal, or p-n junction ? Can I calculate the Potential Barrier by using a workfuncion?

Homework Statement Show that the energy levels of a double square well V_{S}(x)= \begin{cases} \infty, & \left|x\right|>b\\ 0, & a<\left|x\right|<b\\ \infty, & \left|x\right|<a \end{cases} are doubly degenerate. (Done) Now suppose that the barrier between -a and a is very high, but finite...

Homework Statement Schroedinger equation for potential barrier. What if ##V_0=E## First region. Particles are free. ##\psi_1(x)=Ae^{ikx}+Be^{-ikx}## In third region ##\psi_3(x)=Ce^{ikx}##Homework Equations ##\frac{d^2\psi}{dx^2}+\frac{2m}{\hbar^2}(V_0-E)\psi=0## where ##V_0## is height of...

Hi, I have been pondering on this - what is the energy required to move a point mass m0 from a radial position R to the center of a rotating frame, if the linear velocity v of the point mass at position R is relativistic (close to c). For an observer in the rotating frame, it should seem as...

Homework Statement Two conductors are separated by an insulator. Model the insulator as a square barrier of height 0.01 keV and a width of 5nm. Determine the transmission coefficients for electrons of 7,000 meV. The only thing is I have to use the approximation formula for finding the...

I have always understood (As well as I can) potential barrier questions, but this one has stumped me, and I was hoping someone could point out where my thinking has gone wrong. The wave function of an electron of mass m incident to the step from x = -∞ with energy E < V is = eikx + ρe-ikx for...

Tunneling from Rectangular barrier - Exponential Decay ?? Consider the Rectangular Potential Barrier. If one solves bound state Problem in this case, wavefunctions of Exponentially Decaying and rising kind are found for the Region in the Barrier. ψ = A eαx + B e-αx Yet Most Books and...

I want to know that when a pn junction diode is formed and barrier potential is setup then how can we determine the same theoretically. Also I wan to know that is there any relation between barrier potential and energy band gapSmall band gap small barrier? ?

I have a question that's driving me insane and I'm sure there's a simple answer that I'm missing for some reason, but I'm not getting my a-ha moment. Consider 2 cases from intro QM: Infinite square well Potential barrier with E > V0 For the infinite square well, the Schrodinger eqn...

Homework Statement An electron of energy E = 2.2 eV is incident on a barrier of width L = 0.7 nm and height Vo = 3.2 eV as shown in the figure below. (The figure is not drawn to scale.) What is the probability that the electron will pass through the barrier? The transmission probability...

Homework Statement Consider a resonant tunneling diode structure (attached image). This shows 2 AIAs barriers of height 1.2 eV and width t = 2.4 nm, enclosing a well of width L = 4.4 nm. If the effective mass of the electron is taken as 0.9 times the free electron mass how many separate...

1. The Problem Statement An electron of effective mass m* = 0.2me and energy E = 0.1 eV hits a barrier of height 0.4 eV and width t = 5 nm. What is the probability of transmission through the barrier? Use the simplest estimate which is an exponential function. Homework Equations I think...

Hello, first post, don't know if I got the section right tough.. Basically I was wondering, if the efficiency of radiant barrier (for home insulation or industrial, high T) could be improved with different surface geometry eg wavy, triangular, pyramids? Why I'm wondering - the reflective...

Homework Statement A ball of mass m moves horizontally with speed 20 m/s towards a smooth barrier xy which makes an angle tan-inverse(4/3) with the horizontal.The coefficient of restitution is (3/4) find (i) The speed of the ball after the impact (ii) The magnitude of the impulse due to...

Hello Everyone, We know how a schottky barrier forms with a depletion region of width 'W' and contact potential 'qV' as shown in below figure, http://homepage.ntlworld.com/beehive77/images/ntypeschottky.jpg The depletion width 'W' depends mainly on doping concentration of the...

Homework Statement A particle of total energy E is incident on a potential barrier V0 (E<V0) between x=0 and x=a. Write down the allowed eigenfunctions in the regions x<0, 0<x<a and x>a in terms of five unknown constants A, B, C, D and F where A and F are the amplitudes of the incident and...

Homework Statement Use the boundary conditions to show that \frac{A+B}{A-B}=\frac{k_1}{k_2}\frac{C+D}{C-D}=\frac{k^2_1}{k^2_2} Homework Equations A+B=C+D and k_{1}A- k_{1}B = k_{2}C- k_{2}D C e^{i k_{2}L}+D e^{- ik_{2}L} = F e^{i k_{1}L} and k_{2}C e^{ ik_{2}L}- k_{2}D e^{-i...

I was just wondering if anyone here had any experience with an open pipe system with a barrier imposed. Basically, say for a pipe open at both ends, at one end we place a barrier a distance away from the pipe. How would this affect the resonant frequency of the pipe? From experimentation...

It isn't classic homework with classic task or only theory. It is a interesting example of my friend. So, I think it is good to gave it there... I do not understand this very much, I prefer to astronomy, but I am interested it. Can a plane before a barrier (as shown) and stay put when the...

Homework Statement A nuclei of a atomic number Z decays into a alpha particle (a He nucleus with Z =2) and a daughter nucleus with (Z_{d}). The decay may be described as the tunneling of an alpha-particle through a barrier caused by the Coulomb potential between the daughter and the...

This is a question someone asked me today and it's bugging me allot. If the acceleration caused by gravity is greater than the speed of light at a black hole event horizon then does this mean that the matter is falling at faster than light speed?

Hi PF, What is the conceptual difference between potential barrier and potential difference? both have an electric field associated with it. so is potential barrier a sort of potential difference itself and will it cause current flow in a closed circuit like diode shorted. Also why cannot we...

Basically I'm trying to find out how to find the maximum distance between two deuterium nuclei in order to overcome the coulomb barrier, causing them to fuse. Thanks

Why is it that neutrons evaporate from nuclei more easily than protons do? Intuitively, since protons are electrostatically repelled (in addition to whatever nuclear forces they have in common with neutrons), one would expect protons to be ejected more readily than neutrons. (Maybe this is...

Hey all! I am gearing up for next year to do a senior project, I want to knock it out in my spare time for the next 10 months. Ideas are: 1) Laser guided missile- 2 phase motor, one to go up then again to go to 'lazed' target. 2) Wifi barrier- setup focused jammers to create a 'wall'...

Homework Statement Infinite Potential Barrier particle moving in one dimension is incident upon a potential barrier given by V (x) = Gδ(x) where δ(x) is the Dirac delta function and G is a constant with units of energy times distance. (The delta function must have units of inverse distance...

Homework Statement http://img543.imageshack.us/img543/4598/photosfr.jpg Find dss, dsr and thus hs. Homework Equations trig The Attempt at a Solution dss = hs/(sin[θ]) dsr = hs/(sin[∅]) dss = 3.059/(cos[θ]) dsr = 47.191/(cos[∅]) θ = arctan(hs/3.059) ∅ = arctan(hs/47.191) I have tried...