Uncertainty principle Definition and 528 Threads

I came up with a scenario in which I think I am violating Heisenbergs uncertainty principle. Say I build a velocity selector, like the ones found in mass spectrometers, and I fire electrons from an electron gun through it. By measuring the Electric and magnetic fields, I can measure the...

Hey, Sorry, but I have a qustion on the uncertainty principle to join the many others. Just reading a book on physics, and its says that, as a result of the Heisenberg uncertainty principle, if the proton and electron were confined to the same volume of space, the electron would be traveling...

Using the meager physics knowledge I've scrapped together over my 19 year life span I've arrived at the following conundrum. It's more than likely that I'm entirely wrong, but I'd like to know why. Anyways here it goes. First let me unviel my understanding of the universe, limited though it may...

Hallo, Why does dp*dx>>h represents classical mechanics state? Thanks, Omri

I saw a rather easy proof of the Heisenberg Uncertainty Principle in a PDE textbook the other day, but I'm not sure if it's correct. The proof goes as following: Note that \left| \int xf(x) f'(x) \right| \le \left[ \int |xf(x)|^2 dx \right]^{1/2} \left[ \int |f'(x)|^2 dx \right]^{1/2} , by the...

Please, can someone explain how uncertainity principle explains the wave-particle duality nature of matter and radiation.

Homework Statement For an electron in a hydrogen atom: in state psi(100): find (del-x)(del-p) where del x = integral of :[psi (x-<x>)2 psi]dv and del p = integral of: [psi(p-<p>)2 psi]dv Homework Equations The Attempt at a Solution i attempted to multiply out both...

Homework Statement Hey guys. I have this kid throwing a ball with mass M and from high H. He is trying to hit a crack in the floor. I need to show that in order for the ball not to miss the crack, the minimal width of the crack (delta x) should be the expression in the red box in the...

Homework Statement Consider the wave packet defined by psi(x) = integral(limits of +infinity and - infinity) dke^(-alpha(k-k_0)^2) e^(ikx) a)What is the mean value of the momentum p barred (it's just a line over the p) of the particle in the quantum state given by this wave function...

Could someone explain the Uncertianty Principle? Please and Thank you!

Hello all I have a question concerning The Heisenberg Uncertainty Principle. The principle mathematically looks like this- \Delta x\Delta p \geq \hbar/2 The principle states that you can not measure more than two quantities simultaneously. If you know a...

I found the uncertainty between delta x (position) and delta H (Hamiltonian) to be greater or equal to (h_bar*<p>)/ 2m. Does this mean for stationary states, where <p>=0, the uncertainty can be zero? ie we can precisely measure the position and energy?

Homework Statement A 52.9 g ball moves at 12.2 m/s. If its speed is measured to an accuracy of 0.04%, what is the minimum uncertainty in its position? Answer in units of m. Homework Equations delta x times delta p = 1/2 (h/2pi) The Attempt at a Solution I used the...

Sound waves of 499 Hz and 506 Hz are superimposed at a temperature where the speed of sound in air is 340 m/s, Now the question is what's the lenth delta(x) of the wave packet in meters?

Hey what's the relationship between the width of emission lines and the uncertainty principle? My lecturer mentioned it briefly but didn't go into it. I think I get it but would have trouble explaining it. Cheers, nSlavingBlair

Homework Statement Hi all i am doing past exam paper questions and this question i am not sure about, i check notes and books but can't find relevant information Q1i.) If we try to confine an electron in a small region of size a, then this electron has to have a non-sero average kinetic...

Hi! I've just begun reading a textbook about quantum mechanics (by Wolfgang Nolting - a german book). And before the real quantum mechanics stuff has actually started I am already stuck at the first two small exercises at the end of the introductory chapter (despite the solutions being included...

Suppose Fuzzy, a quantum-mechanical duck, lives in a world in which h = 2pi J.s Fuzzy has a mass of 2.0kg and is initially known to be within a range of 1.0m wide. (a) What is the minimum uncertainty in his speed. delta(x)delta(p) = hbar/2 hbar/2 = 1/2 delta(x) = 1 p = mv = 2v so...

Homework Statement Particles pass through a single slit of width 0.2 mm in a diffraction setup. The de Broglie wavelength of each particle is 633 nm. After the particles pass through the slit, they spread out over a range of angles. Use the Heisenberg uncertainty principle to determine the...

Homework Statement Suppose you want to measure the position of an electron to within 1 angstrom. If you also want to measure its momentum, how accurately can you do this if you don't want to mess up your measurement of its position? Homework Equations An angstrom is 1 x 10[SIZE="1"]-10...

What happens if the momentum distribution (sigma p) equals zero. Say the expectation value for the momentum (<p>) and <p^2> are zero. Then you will get 0>or=h/4Pi. How can this be possible? Or vice versa, what if sigma x equals zero?

Homework Statement Using the uncertainty principle find the energy required for the electron to be confined inside the hydrogen atom. Use the radius of the atom 1 x 10-10 m for Δr. Express your answer in eV, rounded up to the nearest hundredth. Homework Equations ΔxΔp\geqh/4pie...

Homework Statement Using the uncertainty principle find the energy required for the electron to be confined inside the hydrogen atom. Use the radius of the atom 1 x 10^-10 m for Δr. Express your answer in eV, rounded up to the nearest hundredth. Homework Equations Δx(Δp)\geqh/4pie x=...

Does this suggest that the 2nd law of thermodynamics has a quantum mechanical origin?

As the above principle says, momentum and position can't be known both at the same time (Δx Δp ≥ h/4π); I am trying to find another example and I was thinking of energy and time following Einstein's box example...does anyone have an idea on whether it'c ocrrect or just another example?

ok so i sort of understand this principle and how to visibly identify an electrons exact location in the space it occupies you have to shoot a photon off it that has a wavelength the same as or less than the electrons wavelength or something and how that alone moves the electron to a new...

Homework Statement Assuming at time is zero, the wavefunction of a free particle is given as \Psi(x, 0) = \left\{ \begin{matrix} 0, \quad x<0\\ f(x), \quad x>0 \end{matrix} \right. where f(x) is integrable within (0, \infty) Find the time evolution of \Psi(x, 0). Write down...

Why is uncertainty principle said to be a very strange thing? "Heisenberg uncertainty principle states that locating a particle in a small region of space makes the momentum of the particle uncertain; and conversely, that measuring the momentum of a particle precisely makes the position...

Is there any a priori connection beetween the orders of magnitude of e.g. momentum, and its uncertainty? Why do we always assume that the momentum is the same order of magnitude as its uncertainy? I'm referring to all those "back of the envelope" calculations. Thanks

We know the momentum of photon, so it can be anywhere in the universe?

Verify that the uncertainty principle can be expressed in the form , where is the uncertainty in the angular momentum of a particle, and is the uncertainty in its angular position. (You may think of a particle, mass m, moving in a circle of fixed radius r, with speed v) b) At what uncertainty...

Verify that the uncertainty principle can be expressed in the form http://www.colorado.edu/physics/phys2170/phys2170_spring96/hws/2170_hw73.gif,[/URL] where [PLAIN]http://www.colorado.edu/physics/phys2170/phys2170_spring96/hws/2170_hw74.gifis[/URL] the uncertainty in the angular momentum of a...

If \Delta x \Delta p > \frac{\hbar}{2}, what happens at T=0? Since "all motion stops" must we have \Delta x diverge? Or is the zero-point motion allowed to occur at T=0, and only classical kinetic energy is zero?

Does the uncertainty principle apply to nature itself or only to the results of experiments? That is, is it the position and momentum that are really uncertain, or merely our knowledge of them? Does it make any difference?

Homework Statement In order for a neutron can exist in a nucleus, its wavelength must be smaller than the size of the nucleus (say 2 x 10-15 m) Use the uncertainty principle to calculate and show that a neutron would have a kinetic energy much smaller than its rest mass energy Homework...

Any guidance towards designing an expiriement/lab/activity related to Heisenberg Uncertainty Principle? It doesn't have to be complex or anything, just something at least related to the HUP. I can't think of anything, my understanding is that this principle only really applies at the quantum...

Today I was assigned a question (that is due tomorrow) and I currenlty have very little idea how to solve it... Any help to get me started here would be greatly appreciated. 1. Use the uncertainty principle to estimate the uncertainty in energy of a proton confined to a nucleus 1.0 x 10^-14m in...

Homework Statement A particle of mass m is confined to a one-dimensional region of length a. a.) use the uncertainty principle to obtain an expression for the minimum energy of the particle b.) calculate the value of this energy for a 1g bead on a 10 cm wire, and for an electron in a region...

I have always had a problem with the concept of "you can't know" and because of that I have always had a problem with the uncertainty principle. Because people much smarter than me have fought this issue longer than I have been alive, and I because am not really qualified to have an opinion I...

The classic physics problem example of symmetry breaking is a pencil sitting directly on its tip (pointed down), but it's possible for the pencil to balance on its tip if we reduce the thermal fluctuations to zero by cooling it to close zero degree. Quantum fluctuations require/mean that...

Hi all While watching the first stage of the Tour de France, I thought of Heisenberg and his Uncertainty Principle. Does the Uncertainty Principle also work in the macroscopic world? I.e., can I tell with 100% accuracy how fast a car is going and where it is? Regards, Niles.

I'm trying to figure out why exactly we have it. It's just a simple question. Do we have this principle because human error is far to great to ever measure a particle's momentum and its location at the same time, or we just can't measure them accurately because they're without our dimension...

Does the uncertainty principle contradict the idea that an object can be at rest relative to an observer? For example, in physics class we examined an electron in a box, and we assumed the walls of the box are stationary relative to the observer. But the uncertainty principle says delta p...

I learned about this in class and some parts have been bugging me for a while. I am to understand that because were dealing with such small and minute measurements, that if one were to attempt to measure values that the experiment would mess up the values read. That it is "physically"...

A measurement establishes the position of a proton with an accuracy of ±1.00 x 10 ^ -11 m. Find the uncertainty in the proton's position 1.00s later. DE Dt ≥ h / 4 ∏ Dx Dp ≥ h / 4 ∏ using DE Dt ≥ h / 4 ∏ DE = 5.276*10^-35 J where t = 1.00s I am stuck as...

Homework Statement Suppose optical radiation (gamma = 5.00 x 10^-7 m) is used to determine the position of an electron to within the wavelength of the light. What will be the resulting uncertainty in the electron's velocity? wavelength = 5.00 x 10^ -7 m mass of electron = 9.11 x 10^ -31...

I have a puzzle I seem to be unable to answer satisfactorily. It concerns the 'Uncertainty Principle': If you can locate a particle (any kind of quanta) at a given location within an uncertainty of deltaX then the uncertainty in its momentum deltaP must be at least h-bar/deltaX. (Please don't...

Homework Statement See lower down for question Homework Equations The Attempt at a Solution I have been trying to find help with this question on the net and in my textbooks. I am really struggling with QM, i don't know where to start - i appreciate what the graph of the...

we have the relation p= E*C then why do we say that we cannot measure momentum accurately? if we know E then we can find p, and then we can find position at ease,whats more difficult here? are we confusing with uncertainty principle? or is Uncertainty principle confusing us? Or am i missing...

i have always read in almost all sites that we have to shine at least a photon to measure the particle's position and momentum and hence comes the uncertainty principle...why we are using this shining photon technique always...is this the only way of measuring particle's position and...