Uncertainty principle Definition and 528 Threads

Is this explanation of uncertainty principle from wikipedia correct? Is this "compressing" the Fourier series/integral? Because the function is not periodic, and with infinite frequencies some of then would put make the speed greater than c "According to the de Broglie hypothesis, every...

Homework Statement I don't know how to do 13.10 and 13.11 http://a367.yahoofs.com/hkblog/LR5wVsiTBB9XH4KDYpBfXDI-_9/blog/20110511014559607.jpg?ib_____DMAbgW2U6 The Attempt at a Solution I just can't get the answer. Can you show me the details of the proof and the steps to the...

It seems the book makes a mistake. Uncertainty principle states: (Uncertainty of p) times (uncertainty of x)>=(a constant) But in the following picture, the writer calculates the exact value of momentum and find uncertainty of x. Is it wrong? I am using Understanding Physics written by...

Some people suggest that free will is proven by the heisenburg uncertainty principle, which states that you can not predict the outcome of a quantum event. Does this mean that humans can some how consciously tell every electron in their body how to act in order for their desires to be fulfilled...

Warning: My understanding of physics is minimal let alone Quantum Mechanics so please excuse (but feel free to correct) my misunderstandings. My understanding of the Uncertainty Principle is that because photons have to hit a particle so that we can view it, we can never be certain of...

Homework Statement show that |\DeltaE/E| = |\Delta\lambda/\lambda|<<1 Homework Equations \DeltaE>hbar/2pi\Deltat \lambda=hc/E The Attempt at a Solution dunno where to start.

I think I undetstand the role of the uncertainty principle in explaining the existence of interference patterns in the double slit expt with electrons i.e. the slits reduce the uncertainty in position and consuequently there is a greater uncertainty in momentum which results in interference...

1. Homework Statement [/b] 1)for an object of size 0.5 Angstrom, what is the longest-wavelength photon with which it can be observed? 2)for the object of problem 1, what is the smallest-energy electron which can be used to make the measurement? Homework Equations 1)\Deltap x \Delta x \geq...

Does the Uncertainty Principle apply to the calculation of particles in a past point in time? As in, can we know the momentum and position of a particle in the past?

Hydrogen Atom ---> Uncertainty Principle Hey guys, I'm having some trouble with this one. [PLAIN]http://img849.imageshack.us/img849/2039/physhw.jpg How do I get started?

Homework Statement \phi(x) is in Schwartz space, and {\int|\phi(x)|^2dx=1. I need to show that (\int_{R^n}|x|^2|\phi(x)|^2dx)(\int_{R^n}|\xi|^2|\phi(\xi)|^2d\xi)\geq \dfrac{n^2}{16\pi^2}Homework Equations Heisenberg uncertainty in one dimension...

I'm trying to get my head round this. I don't see why our inability to measure the world around us means that at the quantum level things must be random. I understand that measuring momentum of a particle to a high degree of accuracy means losing accuracy in it known position. But I don't...

]How can H.U.P be used to explain the following : (i) The non-existence of the electron in the nucleus. (ii) The existence of protons, neutrons and alpha particle. (iii) The existence of finite zero point energy. (iV) The binding energy of an electron in an Hydrogen atom is of the order of 15...

Hi folks, I do read some of the interesting post on this forum particularly the discussions on the concept of uncertainty principle ie the more you know about the particle position the less you know about its momentum etc etc I am a complete novice and am trying to get the big picture here...

We all know that our universe is headed towards a heat death with maximum entropy and useless energy. However, we know that a vacuum of space will always have energy greater than its local minimum (potential well) due to the uncertainty principle. There must always be random fluctuations...

Two observers A and B are in relative motion with a constant velocity[for example, along the x-x' direction].If A knows the the position of B accurately , the motion of B gets enormously uncertain[and vice verse] in his calculations/considerations.How is he going to derive the Lorentz...

We all know that you can supposedly never know the exact position and momentum of a particle, because the very act of measuring disturbs it. Now, why can't we have two particles that start out and evolve the same exact way but separately and, using one of them as a dummy, perturb it, extract...

I have a few questions regarding how/when to use which uncertainty principle formulas. I am not sure of the difference between them. I've checked my book and wiki and neither really helped. Here are the formulas in question. \Delta p \Delta x \approx \hbar \Delta p \Delta x \geq...

The Uncertainty Principle is an inequality relation but while its application, only the equality is considered. For example - to calculate the Mass/Energy of a particle produced during an interaction, the Life Time of the particle is used to divide the Constant (h/2). But in principle the...

I had a thought going in my head today about the uncertainty principle. Forgive me if it sounds too silly. Consider an electron in motion. Now, suppose that I'm measuring it's position with infinite accuracy. So, by the uncertainty principle, it's velocity is blurry. But what if I measure the...

I am trying to understand fully the concept of this principle. But this uncertainty stuff confuses me. Can someone give me the link, or some material so I can work mathematics behind this mechanism. Its not that principle it self is the problem, I have glimpse what's going on, but the...

Analogous to the uncertainty relation ΔpΔx > h/4π, there is an uncertainty relation for the time and energy, ΔEΔt > h/4π that stems from the methods usually used to measure the energy. The uncertainty in the time, Δt, can be interpreted as a lifetime. The excited state of an atom responsible...

Homework Statement Using the uncertainty principle, estimate the minimum energy in electron volts of an electron confined to a spherical region of radius 0.1nm. Homework Equations delta-x * delta-p = h-bar / lamda delta-y * delta-p = h-bar / lamda delta-z * delta-p = h-bar /...

Hi together ... In many textbooks on particle physics i encounter - at least in my mind - a misuse of the Heisenberg uncertainty principle. For completeness we talk about \Delta p \Delta x \geq \hbar/2 For example they state that the size of an atom is of the order of a few Angstroms...

in Heisenbergs uncertainty principle, how do you know when to use hbar, h, h/2 or hbar/2? thanks

Ok hey forum. I thought it might be a neat idea to contemplate this idea, and perhaps regurgitate some thoughts back on to this thread. So, as the Heisenberg uncertainty principle states, one can not know both the velocity and position of a particle or electron. I was curious to hear thoughts...

Homework Statement A beam of 50eV electrons travel towards a slit of width 6 micro metres. The diffraction pattern is observed on a screen 2m away. Use the angular spread of the central diffraction pattern (+/- lambda / slit width) to estimate the uncertainty in the y-component of momentum...

Hi, I am currently having problems solving a an exercise: Let's make the assumption of the existence of an operator H such as [T,H]=i \hbar I. by examining the state: |\psi\rangle}=He^{i \alpha T}|E\rangle} with H|E\rangle}=E|E\rangle} show that the spetrum of H is not bounded below.

Okay I actually have 2 questions. 1) ΔxΔp >= h / 2π Is x one dimensional? Say if I wanted to locate the certainty of an electron in a hydrogen atom with a diameter of 10e-10 m. The electron is confined to the volume of the atom, not just the diameter, so could I say Δx = 10e-10 or...

hi, I do wonder if the Higgs boson is a quantum object because since it is the (only) particle with spin 0, then it should not behave like a wave(since the wave aspect is connected to the fact that it is spinning) and therefore not experience the uncertainty principle. Or am I wrong?

Homework Statement See q attached Homework Equations The Attempt at a Solution Am i right in thinking that the answer to both questions is yes? Neither of the commutators [p, V(x)] nor [x, H = + or - ih.. therefore is the answer to both a and b yes?

Hi, I've just worked through a derivation of the H.U.P. that uses the Cauchy Schwarz inequality to come up with the expression (\Delta A)^2(\Delta B)^2 \geq \frac{1}{4}|<[A,B]>|^2 . This much I am happy with, but then it seems that when dealing with two "canonically conjugate observables" you...

Hi! So I know what the Uncertainty principle states and everything, but I can't find anywhere the "causes" of the uncertainty. Like, what is it exactly that "causes" the uncertainty. If it's not the measurement tools/technology, then what is it?? Please explain in terms of physical phenomena...

Homework Statement http://img219.imageshack.us/img219/306/prblem.png (oops, that line should end with "just before measurement? (Express your answer in terms of the variances of the two operators)" ) The Attempt at a Solution...

\Delta{x}\Delta{p}, \Delta{E}\Delta{t} and particle spin all have units of angular momentum and have ability to be quit uncertain... Any idea if they have something in common (except the units of measurement)?

Hello, I'm (only) receiving an introduction to Quantum Physics atm, and today our professor argued that the uncertainty principle doesn't have a definite form: the right hand side of the inequality is dependent on the confidence measure/certainty you choose, in other words 95%, 99% certainty...

given 2 unnormalized wave functions: Y1(x)=e^i(x/m) Y2(x)=1/2*[e^2i(x/m) + e^3i(x/m) + e^-2i(x/m) + e^-3i(x/m)] if the positions of the particles were measured, which would be found to be more localized in space? (that is, which has a position known more precisely?) to my...

in what scale can we consider the uncertainty principle?can it be considered in the non atomic scale?

Show that for a free particle the uncertainty relation can be written as (Delta lambda) (Delta x) >= lambda^2 / 4pi Firstly I am sorry not writing this in latex but I gave up after trying to write it in latex for half an hour. Would be great if anyone can show me how to do it. Using...

Since we know the precise velocity of any photon, does that mean it's location is always undeterminable?

Hi, I have taken an introductory undergraduate QM course, solving for different boundary conditions like particle in a box, but the physical interpretations of some of the tenets was not well explained. I was surprised to find this paragraph on Wikipedia: "Published by Werner Heisenberg in...

Does the uncertainty principle apply only to electrons or other particles as well?

I am a little confused by something by something in my physical chemistry textbook. If two measurable quantities do not commute, then an uncertainty relation exists for them. Kinetic energy and position do not commute, and the expectation value for linear momentum in a 1-D particle in a box...

A particle is confined within a spherical radius of one femtometer(10^-15 m)? Its momentum can be expected to be about- 1. 20 keV/c 2. 200 keV/c 3. 200 MeV/c 4. 2 GeV/c How should I go about using HUP on a problem like this one? I tried substituting x=10^-15 meters in px=h/4 pi but the answer...

I have a quite simple doubt. One of the practical applications of Heisenberg's uncertainty principle is given by Heisenberg's microscope. In this thought expt. Heisenberg imagines of a hypothetical microscope in which an observer attempts to measure the position and momentum of an electron...

hi, I have a question about the uncertainty principle. if an electron is in attractive OR repulsive electromagnetic field, is its uncertainty about its position lower than if it is a free electron? I believe particles are more random, with a higher entropy when there is less...

I was reading about this, but I'm unclear on something. Does the Heisenberg principle arise due to limitations in technology? Or is it an absolute physical phenomena that can't be avoided no matter how advanced your measuring tools are?

I've been trying to understand the uncertainty principle and so far the Wikipedia definition has been very good explainig position and momentum relationship, but the aperture size explanation below is beyond me. Any help? "If a large aperture is used for the microscope, the electron's...

I hope a pointer to a speculative post on a blog is OK in this group. But as the posting rules at https://www.physicsforums.com/showthread.php?t=5374 reference a dead page, I was unable to check ;-) (It would be easy to copy and paste that article here, if that is considered desirable to...

There is something (among many things of course) that confuses me with the uncertainty principle as it pertains to position and momentum of a photon. If one shoots a photon of red light, for example, at a screen, one can see where exactly the photon hits the screen so position is known. Also...