Uncertainty principle Definition and 528 Threads

A block is at rest. The block is macroscopic so we can see that it is at rest and where it is, i.e. we know its position with certainty. Suppose we use the Heisenberg Uncertainty Principle to estimate the position uncertainty Δ x. Consider the following argument: Since the engine is at rest...

I saw in some sites that vacuum fluctuations are due to uncertainty principle but i couldn't understand how these two are related...uncertainty principle speaks about the uncertainty about particle's position and momentum..vacuum fluctuations speaks about creation of particle pairs and...

I'm trying to calculate the uncertainty in momentum/direction resulting purely from the certainty in position caused by a small slit, as a function of the slit width. Can anyone tell me if I'm doing this right? Starting with the HUP: dX * dP >= h/4pi dX = the slit width w P = h/lambda...

Both uncertainty principle and double-slit interference are the most important contents in Quantum mechanics. Those days I am thinking about this question: Is there a hidden relation between them? Unfortunately, I couldn't give me a satisfied answer. How do you think about it? Thank you!

Hi. This semester I am taking a Philosophy class (introductory) and a Modern Physics class (introductory) and we just recently (in the latter) began officially learning about Heisenberg's Uncertainty Principle. From the lecture (and other reading I've done), I am seeing that the math for...

My understanding of it: You cannot measure both the location and momentum (as in vector) of a particle and have both be correct to a given percentage, where that percentage is the uncertainty. Lets say I build a long tube. Theoretically this tube is so small that you can send a single photon...

A student is examining a bacterium under the microscope. The bacterial cell has a mass of 0.200 (a femtogram is 10^-15) and is swimming at 4.00 microns per second, with an uncertainty in the speed of 5.00%. E.coli bacterial cells are around 1 micron, or 10^-6 meters in length. The student is...

So I am just beginning to emerge myself into quantum physics. I am reading some things about the uncertainty principle and find myself very confused. Why exactly is locating a particle in a small region of space make the velocity of that particle uncertain and vice versa? I'm guessing...

[SOLVED] Help with understanding the uncertainty principle I may have posted this in the wrong forum. If so I am sure a moderator could move it to the correct one. Problem statement: I have an assignment in which I need to calculate the lowest possible mean of an electron's KE , <KE>, based on...

I have seen different versions of the uncertainty principle. Which is the correct one? \Delta x \Delta p >= h \Delta x \Delta p >= \frac{\hbar}{2}

[SOLVED] Heisenberg Uncertainty Principle question Suppose that the x-compenent of the velocity of a 3.0 x 10^-4 kg mass is measured to an accuracy of plus or minus 10^-6 m/s. What then is the limit of the accuracy with which we can locate the particle along the x-axis? Any help on where to...

If a neutron star is made solely of neutrons that show no repulsion to each other, protons and electrons have merged by overcoming electron degeneracy pressure so all the empty space taken up by electron shells is removed, how do u get anything denser to the level of being a black hole? If a...

[SOLVED] Delta Function Well and Uncertainty Principle Homework Statement Griffiths Problem 2.25. I need to calculate < p^{2}> for the Delta Function Well. The answer given is: < p^{2}> = (m\alpha/\hbar)^2 The wave function given by the book is...

Uncertainty principle is a quite revolutionary concept and go hand in hand with the so-called probabilistic picture of the quantum particle. What is worrying me for last a few days if there has been any attempt---theoretically or, experimentally to check the position and momentum uncertainty...

Homework Statement Is it possible to find out the minimum permitted energy of an electron in a Hydrogen atom and its corresponding mean distance from the nucleus using Uncertainty principle? Homework Equations The Attempt at a Solution I know that if the mean distance is known...

Hello, use uncertainty principle to calculate the minimum energy of quantum osilatore?? who is can help me?? thanks

I need to estimate the amount of time that an ice pick can be balanced at it's tip and the only limitation is set by the Heisenberg uncertainty principle. I assume the tip is sharp and the surface that the tip rests on is hard. I can also assume values of dimensions and weight as long as the...

Hi everybody, I have a slightly noobish question and I've searched for the answer unsuccesfully so I'm posting it here. I'm was reading up on the uncertainty principle when I ran into two phrases that I don't quite understand. They are <A²> and <A>². Am I too apply this as \int \psi^* A^2 \psi...

I find quantum mechanics to be very hard, and I am currently having trobule with the following 2 problems, can someone please help me out? 1) A thin solid barrier in the xy-plane has a 10-micrometer-diameter circular hole. An electron traveling in the z-direction with vx=0 m/s passes...

Let's say a proton is confined to some diameter, d. What would be the uncertainty in the position? In some questions they use delx as (1/2)d as the uncertainty in position. In other cases they use the entire d as the uncertainty. This is extremely confusing...

Homework Statement A proton is confined in a uranium nucleus of radius 7.43 fm. Determine the proton’s minimum kinetic energy K ≥ ∆K according to the uncertainty principle if the proton is well approximated by a Gaussian wave packet confined by the nuclear diameter. Homework Equations...

Prove the uncertainty principle, relating the uncertainty in position (A=x) to the uncertainty in energy (B=p^2/(2m + V)): \sigma x\sigma H \geq \hbar/2m |<P>| For stationary states this doesn't tell you much -- why not??

Homework Statement According the the Uncertainty Principle, an electron of mass m when placed on a 'flat' tabletop will actually 'float' above the table i.e. the vertical position of the electron will be spread out over some distance. Use the uncertainty principle to find an expression for...

Homework Statement According to Heisenberg Uncertainty principle, Del(X)xdel(P) >= h/2(pi) But there is also another expression given in my book which is, Del(X)xdel(P) >= h/4(pi) I asked my lecturer why is it so? She said that, the second...

Homework Statement Suppose the minimum uncertainty in the position of a particle is equal to its de Broglie wavelength. If the particle has an average speed of 4.7 105 m/s, what is the minimum uncertainty in its speed? Homework Equations lambda=h/p & (Py)(Y) is greater than or...

Is this formula is true according to Heisenberg uncertainty principle? the formula that describes the velocity is equal to the change of the displacement over the change of time,,,,, is this formula true according to Heisenberg uncertainty principle? specially it is impossible measuring the...

Hey guys I have a few questions... My book defines the Heisenberg uncertainty principle by ∆x∆Px >= aitch-bar All other resources I have have it stated as ∆x∆Px >= aitch-bar/2. They mention that ∆Px and ∆x represent the rms values of independent measurements. My book represents ∆x...

Can we mix SR and uncertainty principle? for ex. from uncertainty principle we have \Delta x \Delta p \geq h/4\pi . Books then write m \Delta x \Delta v \geq h/4\pi with an assumption that m can be measured accurately. However form SR we know that mass depends on velocity; with mass...

I need to prove that the uncertainty principle can be expressed in the form delta L * delta theta = hbar/2 where delta L is the uncertainty of the angular momentum and delta theta is the uncertainty in angular position. I know that L = m*v*r and I think I can express theta as x/r...

In what ways does Bohr's model of Hydrogen atom violate the uncertainty principle?

I don't get how the uncertainty principle is a direct consequence of wave-particle duality?

Basically, in my two courses on quantum mechanics that I had already, and probably will be the last in-depth study of the subject, I had a certain interpretation of its foundations. Basically, my idea was and is that because we observe a quantum state, the wave collapses, and so, it is our...

I was reading about the derivation of the Heisenberg Uncertainty Principle and how Heisenberg used Gaussian Distributions to represent the uncertainty of position and momentum in his calculation. Why is it that Gaussian Distributions were used? There are many different types of distributions...

Not sure if this should go into a math section, but I am trying to understand it in order to understand the Hesenberg uncertainy principle. I can't find a simple introduction to Fourier series to answer this question. In my modern physics book, it does a quick introduction to Fourier series...

Please paraphrase the Hiesenberg Uncertainty Principle in 100 ACII characters or less? Thanks!

I'm trying to understand the Uncertainty Principle, for the case of momentum and position, but I'm stumped. Suppose one can measure the position of a particle with arbitrary precision. Suppose the measurement of this particle's positions were made at time t= 0 and then time t=1. The...

Hello, Lately, I have been thinking about the uncertainty principle (UP) and how it applies to the nucleons. Now, I understand that the reason that the electrons do not collapse into the nucleus may be explained by the UP. If the electrons collapse into the nucleus, the uncertainty in...

A contradiction of Heisenberg uncertainty principle?? Suppose an atom is cooled to 0 K (Practically impossible). However theoretically, all its motion will cease ; and therefore it will be possible to determine the exact position of the atom and exact velocity (which is zero).Doesn't this...

Hello Folks! Though I have written my own paper (http://arxiv.org/abs/math.DG/0605709) , I am still a novice in Standard Model. Therefore, I have some questions for experts. The modules squares of the fermion wave functions are interpreted as the probability densities for the particles to...

The Heisenberg uncertainty principle says that h-bar/2 <= dE * dt. Let's say we have this device that emitted very low energy radio waves. Does that mean there'd be a significant probability of these photons traveling faster than light?

Most popular or elementary textbook level expositions advance the following physical argument in favor of the uncertainty principle: In order to observe a state we must disturb it. Thus we have changed the state by our very act of observation and uncertainty creeps in. Now this explanation...

Hi, I was wondering about the following question. Does Heisenberg's Energy-Time uncertainty inequality (ΔE.Δt=>h/2) imply non-conservation of energy? I mean, if the total energy of the system fluctuates, then how can the energy be conserved? Does the COnservation of Energy so fundamental to...

Can someone explain why the compton wavelength and event horizon are used to determine the uncertainty in what we can see if we were to look back in time to the big bang. (We can only see back to 10^-43 seconds after the big bang.) Here's a website that derives this time (Planck time)...

The energy of a certain nuclear state can be measured with an uncertainty 1 eV. What is the minimum lifetime of this state? I used (delta_E)(delta_t)=h/(4*pi) and solved for delta_t and got it wrong. Any ideas? Thanks.

I'm having a little trouble with my textbook's explanation. This is regarding the energy - time variation of the uncertainty principle; very basic stuff, so I hope helping me out won't take too much. Let me quote exactly: "... the energy conservation can appear to be violated by an amount...

I am having trouble getting going on this problem and I'm hoping someone can help get me started. I have no idea how to do solve this. Originally I thought about using Heisenberg's uncertainty principle and setting delta x = 1 m. Yet I don't see how the uncertainty in that direction is...

Hi, I try to understand the proof for the uncertainty principle for two Hermitian operators A and B in a Hilbert space. My questions are rather general so you don't need to know the specific proof. The first thing I couldn't get into my head was the definition of uncertainty (\Delta...

question is: use the uncertainty principle to show that if an electron were confined inside and atomic nucleus, diameter of 2 x 10^{-15}m, it would have to be moving relativistically i.e. more than 0.1c. what i have done is the following: \Delta x \Delta p = \frac{\hbar}{2} then i set...

Using the uncertainty principle for energy and time, estimate the range of the Strong interaction if it is due to the exchange of a pion with rest mass 140GeV (Take the value of h as 4.14x10^-21MeV s) Now I know that Delta T x Delta E is > or = to hbar and that I want DeltaX as a solution. But...

Would it be correct to conclude from the Uncertainty Principle that the Newtonian mechanics of being able to exactly determine the velocity of a particle from its displacement (and vice versa) through differential equations is only an approximation? Many fundalmental things in the Universe is...