Uncertainty principle Definition and 528 Threads

Hello All, I want to understand uncertainty principle. I understand that when we measure x accurately we cannot measure p with that accuracy. The process of measuring x accurately might like this: some detector fires high energy photon to that small particle, and we can know x accurately. But...

If a particle gives off its own light, how can we never know its position as well as its momentum, as we can see it and thus measure its speed, and know its velocity? How does the Uncertainty Principle treat this circumstance?

From what I've gathered reading the scientific literature, the more precise we know a quantum system's position, the more uncertain the momentum becomes. Does the uncertainty principle place a limit on how well we can know a system's position when we measure that observable? I've read...

Fairly simple question but it's been bugging me for a while: Particle accelerators such as the LHC publish some impressive images of the tracks of particles in their detectors. Can someone explain why that is possible considering the uncertainty principle?

Hi there, So here's my assignment: ''The velocity of a positron is measured to be: vx=(4.00±0.18)*105 m/s, vy=(0.34±0.12)*105 m/s, vz=(1.41±0.08)*105 m/s. Within what minimum volume was the positron located at the moment the measurement was carried out?'' I think I'm not wrong when I say that...

does the fact that there is a limit on how much can be observed on electrons location and momentum have anything to do with the finiteness and conservation of information? is the total momentum plus location of an electron unknown to us or is it also unknown to the universe? meaning, does...

Homework Statement If a neutron is confined to the nucleus, its wave function – and therefore the probability of finding it at a certain position – has a characteristic width, Δ
x, equivalent to the nucleus diameter. What is the uncertainty in the neutron momentum Δ
p as a function of...

Homework Statement Calculate [x,px] = (xpx - pxx) Do this for a function f(x). Now calculate [x,py] for f(x,y) Homework Equations px is actually px hat, I'm just not familiar with latex code. px= -i (d/dx) The Attempt at a Solution I believe I got the first part, for...

Homework Statement The uncertainty ΔB in some observable B is given by a formula ΔB = √<B^2> - <B>^2. Use this formula to determine the uncertainty in position, Δx, and momentum Δp, for the ground state of a quantum-mechanical particle of mass m is a 1-D 'box' of length a, and show that the...

Homework Statement A particle of mass m is subjected to a potential V(x)=Kx.Use uncertainty principle in the form Δx.Δp≈h(bar)/2 to estimate ground state energy of the particle. The Attempt at a Solution I have no idea. :(

hi my concern is, that there is a huge amount of equations that are somehow related to the uncertainty principle and it is not straightforwardly obvious to me, when i have to use which of them. let me put it this way: as far as i see, there is this overall applicable equation that says ΔxΔp ≥...

If I understand correctly, the uncertainty principle works, because in order to measure the position accurately, you need a smaller wavelength. But observing with a particle with smaller wavelength means observing with a particle with larger momentum. Therefore, when the observation is made by...

I completely understand the uncertainty principle and why we can't pinpoint the exact location of an electron. but what if we could?? would it be important that would could find the location of an electrom? would we know more about atoms?

Is there a mathematical or physical proof for uncertainty principle other than the one that says if you want to observe a particle you should collide with it,a photon and blah blah blah ? I can't accept that as a proof.Because It falls if you find another way of measuring the position of the...

Suppose I have an electron gun that shoots electron with momentum p (no uncertainty) at t=0, then at t=t0 I can calculate the exact location of my electron, with no uncertainty. Violation of uncertainty principle?

[FONT="Courier New"] [SIZE="3"] To my understanding Heisenberg Uncertainty Principle, states that we do not exist due to the fact that atoms("what we are made of") are not present, when they are not consciously observed. Please elaborate.

I'm a bit confused about how the uncertainty principle allows for the spontaneous creation and annihilation of virtual particle pairs. I can understand that energy conservation can be violated for a very short time as per delta_e*delta_t > h_bar/2. However, when the virtual particle pair...

Homework Statement In Bohr model of the hydrogen atom, the max. kinetic energy that an electron can have is around 13.6 eV, as it would otherwise not be confined to the atom. Uncertainty Principle: ΔxΔy ≥ h/2π a) Find the max. momentum of such confined electron. b) Use Uncertainty Principle...

how Energy time uncertainty principle account for the broadening of a level? thanks in advance

Let me first start off by saying that I am somewhat new to physics and it's understanding. But I was looking over the Hiesenberg Uncertainty Princple and a thought occurred to me. The Heisenberg Unvertainty Principle states "More precisely the position is determined, the less precise the...

Homework Statement The linewidth of a certain fluorescing dye molecule is 60nm and the peak emission wavelength is 600nm. The lifetime of the dye molecule in the excited state is 1ns. Determine whether the linewidth of the emission is a result of the uncertainty principle. (it may be helpful...

Hello I know this topic must have been done to death already, but i can't seem to find a satisfying answer. As the title suggests, my question is, what experiment proves that the uncertainty principle is not just a result of our flawed measuring techniques? From what i understand, when we...

Homework Statement Use the uncertainty principle to estimate the ground state energy of a particle of mass "m" is moving in a linear potential given by V(x) = ∞ for x≤ 0 V(x) = αx for x ≥ 0 Homework Equations ΔxΔp ≥ h/2 The Attempt at a Solution I've looked at a similar problem...

Heisenberg's uncertainty principle only seems to have implications for our understanding of the body of knowledge produced by science, not reality itself. The uncertainty comes from the inability to make two separate measurements, since each measurement will disturb the system and change the...

Homework Statement Using Heisenberg's uncertainty principle, calculate the uncertainty in the position of a proton moving at a speed of (5.00±0.01) x 10^4 m/s. Homework Equations Δx\geq \frac{h}{4mΔv\pi} The Attempt at a Solution x\geq (6.626*10^-34)/(4pi(1.6726*10^-24)(5±0.01 *...

I'm trying to understand the Heisenberg Uncertainty Principle, as it relates to experimental measurements, because it's kind of confusing me. We just learned the derivations for it in my QM class -- basically it's two standard deviations multiplied together (corresponding to measurements of...

The uncertainty principle says that you can't simultaneously measure position and momentum with arbitrary precision. So you can measure one at a time t1 and the other at a time t2 with t2 > t1, thus not measuring both simultaneously, but relativity tell us that there exists a frame of reference...

Hi, I was watching Through the Wormhole two weeks ago (I think it was a re-run), and they were talking about the uncertainty principle, and how it was impossible to prove due to the change in momentum of a particle when hit with an observation device, such as light. I think the guy was using...

I understood the Delayed Eraser experiment, and the Eraser experiment and the basic double slit experiment. And all I can conclude is, why? Why is there such a necessity? I now understand that it's most probably impossible to learn the 2 properties at the same time but I don't see any...

If Uncertainty Principle is a result of 'fiddling' of an apparatus with what is being observed (for example light particle/wave of a detector fiddling with particles/waves being observed), then wouldn't uncertainty principle cease to apply if in the future a 'smaller' or 'less interfering'...

I've been exposed to two different interpretations of the uncertainty principle. 1) If an electron is in a certain state, a measurement of its position will yield a definite result. However, if after the measurement the electron could be returned to the same state, then a repeated measurement...

Hi all, I am sure this is a quite simple question but I just can't figure it out, any helps would be greatly appreciated. If a particle stay in a state in a very short time, then by energy time uncertainty relation, it's energy must has a great uncertainty. Also because of energy is propotion...

couple of questions a) the operators not commuting would also be true of position and momentum operators in classical mechanics (x d/dx -d/dx x) f(x) so the non-commutation does not inherently constitute a proof for the uncertainty principle, or do you just not care about the uncertainty at...

Here's how I understand it: The light of a shorter wavelength disturbs the momentum of the electron, but shows the electron's position. Why doesn't the light of a longer wavelength disturb the momentum of the electron?

I've come across an apparent paradox in elementary quantum mechanics, and after a little Googling, haven't found a reference to it. Here goes, The 1-D infinite square well is a classic problem in introductory QM. We find that the position-space eigenfunctions of the Hamiltonian (the "allowed...

You are no doubt familiar with Heisenberg's uncertainty principle, putting a limit on the accuracy with which we can measure a particle's position and momentum, \Delta x \Delta p \geq \hbar/2 On my course I was shown the derivation, it popped out of a few lines of mathematics involving the...

Hello everyone. This is my first post, but I enjoy reading all the forums. I have a simple question that I thought about recently: Would Heisenberg's Uncertainty Principle still hold up if we could somehow observe a particle without the aid of instruments? I know it is entirely...

Ok I feel a bit silly asking about this, but I have gotten myself confused and need some help sorting something out. In QFT the operators of observable quantities commute over space-like intervals, so we cannot propagate effects faster than light, causality is safe, cool. But I have somewhat...

Please teach me this: In Quantum Mechanics the Heizenbeg principle holds for one particle.In QTF Theory,the creation and annihilation operators corresonding to coefficients of Fourier components of transformation,so it seem that each quantum(particle) has a definite momentum.Then it seem that...

It is stated that electrons orbit the nuclei of atoms not as particles. By the Heisenberg Uncertainty Principle (whatever that is) one cannot pinpoint their actual location and one cannot track the motion of an electron as it orbits the nucleus. What is that all about? Please use 10th...

What is Heisenberg's Uncertainty Principle?? Homework Statement Hey everyone, Until very recently, I had always thought that Heisenberg's uncertainty principle was that \Delta x \Delta p \geq \frac{h}{2\pi} (or \hbar) However, I'm doing my final year of high school physics this year...

First: If subatomic particles have momentum, then don't objects at rest have momentum [since they are made of these momentous particles] ? My main question is: If the position of an electron is uncertain, then isn't the position of an object NOT constant? Even to the slightest degree? Thanks...

I am new, and I don't have a physics background, so please excuse the question if it is incredibly easy... Does the Heisenberg Uncertainty Principle mean that we just can't measure the location of an electron to perfect accuracy, but such a location does exit (we just can't know what it is)...

Recently, I have a look of the Einstein's thought experiments challenging the uncertainty principle. One of the experiments is the Einstein's slit. I found the description about it : "Consider a particle passing through a slit of width d. The slit introduces an uncertainty in momentum of...

I have often seen it stated that the Uncertainty Principle (UP) is a unique feature of Quantum Physics, but surely it applies classically too? For example, if someone throws a ball across a room, and I take a photo with a shutter speed of 1 second, the resultant photo will tell me a lot about...

So to determine the position of an object you can scatter light off of it. Fine. But then my textbook says you can't know the exact position of the object because of diffraction effects. We've covered the diffraction of light through narrow slits but I don't know why if you were scattering light...

Homework Statement Heisenberg's uncertainty principle states that you cannot simultaneously know the position and momentum of an object. In this video link, a laser is aimed through a slot and projected onto a wall. As the slot gets narrower, the projection also gets narrower. Eventually...

Hey I'm hoping for some help in understanding the relationship between ##\delta x \delta p \geq h## and ##\delta k \delta x \approx 1##. I know the second describes the relationship between span of a wave packet and the frequencies used in a series representation of a Gaussian function. I...

Homework Statement A neutron in an atomic nucleus is bound to other neutrons and protons in the nucleus by the strong nuclear force when it comes within about 1 fm of another particle . What is the approximate kinetic energy in MeV of a neutron that is localised to within such a region? Take...

This is my first post here, and I just want to add the following disclaimers: I'm not in university, and I have never taken a physics class proper in my life. xD I want to say I understand quantum mechanics in principle, as while I think I understand many of the concepts I do not know it...