Barrier Definition and 260 Threads

Hi Bactriophages can cross the blood brain barrier but do all of them cross? They are very diverse.

"... two physical systems [seperated by wall], A1 and A2. A1 has ##\Omega_{1}(N1,V1,E1)## possible microstates, and the macrostate of A2 is ##\Omega_{2}(N2,V2,E2)## " "... at any time ##t##, the subsystem ##A_{1}## is equally likely to be in anyone of the ##\Omega_{1}\left(E_{1}\right)##...

This has been bothering me for a year. I saw a news report outlining the potential of a flood coming down a street. The street was lined with plastic barricades filled with water to keep the flood waters from getting to the buildings on the street. It seemed to me that since the specific gravity...

When I see explanations for quantum tunneling, the discussion is around the probability of an electron manifesting itself before the potential barrier, and after the potential barrier. However, looking at the curves draw, there is a non-zero probability (the evanescent part of the wave) inside...

In quantum mechanics in books authors discuss only cases ##E<V_0## and ##E>V_0##, where ##E## is energy of the particle and ##V_0## is height of the barrier. Why not ##E=V_0##? In that case for ##x<0## \psi_1(x)=Ae^{ikx}+Be^{-ikx} and for ##x\geq 0## \psi_2(x)=Cx+D and then from...

So, I was reading through this thread: https://www.physicsforums.com/threads/would-a-portable-railgun-make-a-lot-of-noise.985309/#post-6309691 and I managed to make one of my usual questions which need more specific knowledge on the subject than I can find on the web. I (think I) understand...

This is the V(x) diagrams and what I am thinking (really not sure though) is that for the first one you the energy has to reach V2 before it can start transmitting and the graph can take off from T=0, since there is an increase in energy potential that is V2. And as the energy increases, the...

Hi, it's been so long since I learned quantum mechanics. So the only thing I can solve now is the square quantum well problem. But I need help because I have to solve this problem of quantum well. I tried some calculation but not far.I try to draw the capacitance-voltage profile by drawing the...

In Bransden textbook, it is stated that the probability current density is constant since we are dealing with 1-d stationary states. It gives probability flux outside the finite potential barrier which I verified to be constant with respect to x, but it doesn't provide the probability current...

Acoustic barrier fence is an excellent way to add sound absorption to an industrial or architectural environment to reduce harsh reflections from hard reflective surfaces, thereby lowering noise levels

Hello! I'm very interested in knowing your opinion on how close my model is to the Fresnel Diffraction by an opaque barrier, as seen here: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/difopa.html#c1 My model: Sorry for the low quality image.

Let's say the solution on the left hand side is a sinkx + b coskx = 0 We get one solution for each E if we omitted a and another solution if we omitted b. However, how to conclude that they are all the solutions? Will there be any solution of the 5 coefficients such that a and b are both not...

Homework Statement Question_________________________________________________________________________________ Find transmitted coefficient and reflected coefficient in case barrier potential E<V ? determine. ##Ψ_{I} = Ae^{ikx}+Be^{-ikx}## ##Ψ_{II} = De^{βx}+Ee^{-βx}## ##Ψ_{III} = Ce^{ikx}##...

Hi there, I am currently doing a project involving cold-plasma technology systems. I am struggling to find papers relating to surface-micro barrier discharge systems, and the difference between those and dielectric barrier discharge systems. Any help would be greatly appreciated, however basic.

I have 3 questions. After thinking about it I feel these questions may indicate that I have some misunderstanding in basic knowledge or some missed parts. 1. Why is the (time independent) wavefunction an exponential decay inside the potential barrier? I know the mathematical derivation, but I am...

When a car is parked and not running... is the radiator water (or coolant) pump totally shut that water from the radiator side can't enter the engine or in equilibrium (what's the exact term)? The water pump is a centrifugal pump.. does this totally shut the inlet and outlet from mixing so that...

I am having trouble in making a power source for the DBD. I can't seem to find any calculations to get the required voltage and frequency of AC to generate plasma. I want to know the circuit/method/equipment needed to generate that voltage from a normal 220 V/50 Hz AC socket in my lab.I am doing...

Homework Statement How to calculate the Coulomb barrier between a proton and a lithium nucleus. The variable is r (interaction radius). The known data is Z1, Z2, k (Coulomb constant), and e (elementary charge). Homework Equations The equation is UCoul = kZ1Z2e2/r The Attempt at a Solution I...

Homework Statement The probability for a particle of energy E<<V0 to penetrate a potential barrier of height V0 and width d is approximately \frac{16E}{V_0}exp\left[\frac{-2d\sqrt{2m(V_0-E)}}{\hbar}\right]. An electron moves between two potential barriers of height V0 and 2v0 that are of widths...

Hallo all, I'm investigating in using a dieletric barrier discharge for gas treatment, if I have two electrodes isolated by dieletric and the discharge gap between both of them has AIR.. how the ionization of air will take place, from where the source of electron which is going to start the...

For a proton striking an atomic nucleus (in a Cockcroft-Walton accelerator, for example), the Coulomb barrier must be overcome. The calculation of the Coulomb barrier is U = k Z1Z2 e2 / r r is interaction radius. How can I find that? For a proton to enter the atomic nucleus what would it be?

Hey there! We started Lab III last week, but things are a bit... strange. See, those exercises were written back in the early 1900s,and so they ask us to read from a book that was published around 1890 or so. Naturally, the library has only one copy, and it's open for 2hours per week, so it's...

Homework Statement Suppose we have a potential such that $$ V = \left\{ \! \begin{aligned} 0 & \text{ if } x<0\\ \mathcal{E}x & \text{ if } x>0, x<L\\ \mathcal{E}L & \text{ if } x>L \end{aligned} \right. $$ for some electric field ##\mathcal{E}##. I'm trying to find the transmission...

Hi all, (See attached image file) Two mutually coherent and collimated light beams intersect as shown, creating the stationary 'bright' and 'dark' fringes of fig.A. Suppose that, after the fringe pattern has formed, we insert a very thin (compared to the fringe-width) and (ideally) perfectly...

I learned that for nuclear fusion to take place, particles must overcome the electrostatic field but what exactly is it? And how is it created/formed?

In a barrier potential with sections: I: V(x)=0 (x<-a), II:V(x)=V (-a<x<a) and III:V(x)=0 (a<x) you can write the solution in this form: Ψ(x)=Ae^(ikx)+Be^(-ikx) (x<-a) Ψ(x)=Ce^(ik'x)+De^(-ik'x) (-a<x<a) Ψ(x)=Ee^(ikx) (a<x) and with boundary conditions solve, but why do you can write this...

Let us consider the following thought experiment. There is a magnetic field in free space produced by a steady current, hence solution of the (magnetostatic) Ampere's law Curl H = J. There is also a material with some parameters ε and μ and no currents, where the Ampere's law is Curl H = 0...

Hi. I understand that in 1-D when E< V(minimum) there exist no physically acceptable solution to the Schrodinger Equation. I have been looking at delta potentials using Griffiths book. I follow his working for the delta potential well but when it comes to the potential barrier I don't understand...

I read phys.org and science daily, daily. I read about all these amazing experiments and discoveries and I want to try my own experiments. A lot of articles are about emerging computing technologies, and often the article emphasizes how inexpensive these materials and processes are becoming. I...

According to quantum theory it is possible for a particle to diffract around a barrier. Does this explain why I often seem to completely miss a tennis ball? Explain why or why not?

Homework Statement A ring charge of total charge Q and radius a is concentric with a grounded conducting sphere of radius b, b < a. Determine the potential everywhere. The ring is located in the equatorial plane, so both the sphere and the ring have their center at the same spot. Homework...

[this thread was moved from the Quantum Physics subforum, hence no template] In this page : http://www.physicspages.com/2012/08/06/finite-square-barrier-scattering/ When the E<V The boundary condition tells us the equation (9) (10) and (11) (12). I tried to get the results from those equation...

Can you gurus help me understand in a qualitative way the nature of the Coulomb barrier as it applies to alpha decay? I can intuitively appreciate the Coulomb barrier as it applies to anincoming charged particle, but resources I have been reading apply the same term to the barrier felt by...

Interesting article on bicycle physics and researchers who've investigated it: http://www.scientificamerican.com/article/the-bicycle-problem-that-nearly-broke-mathematics/

Homework Statement Sorry for the dull question. Problem is as shown/attached Homework Equations The waves in part ii) are traveling in a HIL dielectric of permittivity ##\epsilon_{r}## from ##0 <z<d## and then hit an ideal metal boundary at ##z=d##. The Attempt at a Solution I figure this...

Homework Statement Using the diode equation with moderate forward bias, show numerically how to find the Schottky diode barrier height and the ideality factor via a graphical plot. Homework Equations I = I0e(eV/nkT) I0= AA*T2e-eφb/kT with n= ideality factor and φb= Barrier height The Attempt...

Homework Statement Explain why large transport trucks have a hard steel barrier between the load and the driver's cab. Consider Newton's first law in your answer. Homework Equations no equations required.The Attempt at a Solution According to Newton’s first law, if no net force acts on an...

Homework Statement Consider a one-dimensional, non-relativistic particle of mass ##m## which can move in the three regions defined by points ##A##, ##B##, ##C##, and ##D##. The potential from ##A## to ##B## is zero; the potential from ##B## to ##C## is ##\frac{10}{m}\bigg(\frac{h}{\Delta...

according to einstien, I order for an object to move faster than the speed of light, we need an infinite amount of energy. Assuming that we could somehow generate this much energy, after moving faster than the speed of light, would the hypothetical particle generate a build up of light waves...

Homework Statement Consider a one-dimensional time-independent Schrodinger equation for an electron in a double quantum well separated by an additional barrier. The potential is modeled by: V (x) = -γδ(x - a) -γδ(x + a) + βδ(x) Find algebraic equations which determine the energies (or...

Hi, In transmission coefficient T= exp(-2sqrt(2m(U-E)/hbar^2)L), L, as I interpret it, is the distance of the potential barrier. I am wondering if I have N particles all with kinetic energy E, approaching the barrier, can I integrate the transmission coefficient over a distance from infinity to...

The usual way to explain the formation of a Schottky barrier between a metal and semiconductor is the following: Suppose a metal and a semiconductor with different work functions are put into contact. To compensate for the work function difference ΔW of the two materials a charge layer will...

Homework Statement Electrons are pushed into a grounded metal tube A by the kinetic energy of 100 eV. After having gone through the tube it passes into another tube, B, at some distance from A. Tube B is kept at a potential of -50V. Calculate how many of the electrons are reflected back into...

The following code compares my result to the known correct result. Can anyone find where my error is? If you run the octave code you will see that my answer has positive concavity whereas the correct one has negative concavity...I've checked this so many times and can't find my error. I wanted...

Homework Statement Rectangular barrier of width a and height V0 with an E < V0. What is the transmission ratio, T? Homework Equations T = C*C/A*A What am I missing in my attempted solution (variable name = TChip), which is different from the known solution (variable name = TSoln)? The Attempt...

I'm trying to work out an analytical approach to plotting fission barriers of heavy atoms as a function of angular momentum. I've visited some articles but I have found no way of calculating it. Has anyone any ideas?

A particle of energy ##E## is incident upon a potential barrier of potential ##V_0## and of thickness ##a##. Given that ##E>V_0##, the transmission coefficient is given by If destructive interference occurs when the path difference between the two reflected waves (at points ##x=0##...

There have been some stories in the news lately about using focused ultrasound and collapsing bubbles to open the blood-brain barrier and deliver drugs to treat a brain tumour. e.g. here I was actually involved in the early stages of this project, working on theory and simulations. I wrote a...

The energy of an incident charged particle refers to its kinetic energy. What does the potential barrier energy refer to qualitatively? EDIT: Is it just in reference to the "potential barrier" in the classical sense? where if the particle has less than the energy V, then it doesn't go through...

Homework Statement It is a potential barrier with E of the incoming matter wave E>U (greater than the height of the barrier). I have already done a LOT of algebra to get to the point where ##\frac{F}{A}=\frac{2kk'e^{-ikL}}{2kk'cos(k'L)-i(k'^{2}+k^{2})sin(k'L)}## which I won't bother writing...