Uncertainty Definition and 1000 Threads

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 This is from a laboratory exercise. I was asked to measure the time it took for a pendulum to cover 3 periods. I repeated this 25 times, to get 25 measurements for as many trials. I also calculated the standard deviation from the measured data (calculated for different...

Determine the absolute uncertainty of the prism's volume. The uncertainty of each measurement is +/- 0.5mm. The length of the prism is 142mm, width is 86mm and the height is 151mm. Thank you!

Hi folks, I am new to physics forums , an engineer by profession, I have newly developed some interest for pure physics, can someone please enlighten me on the violation of energy conservation by the time energy UP? The way I understand it the principle only puts a LOWER bound. Is...

What's Really so "Quantum" About Heisenberg's Uncertainty? I've never really understood what was so interesting and strange about Heisenberg's Uncertainty (or Robertson's Inequalities). If we take as axiom that particles exist as wave functions that satisfy schrodinger's equation then what is...

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 /...

Given the state and an operator I know the uncertainty of this operator can be calculated via (see next post latex is being weird, sorry)

I am new to XRD and want to know the best way to measure uncertainty. Any help would be greatly appreciated.

I am looking at the paper "The uncertainty principle in the presence of quantum memory" by Berta and others. It states that if Bob maximally entangles a particle P with a quantum memory M then he can beat the bound of the uncertainty principle on P. The argument is that, if Bob gives P to...

If buckyballs display uncertainty in the double slit experiment, shouldn't iodine gas molecules as well? An I2 molecule is certainly less massive than a buckyball. Yet why can we see I2 gas as a purple haze? I can see it, almost in the same way I can see my pencil, which has a very small...

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...

Whenever I hear the Uncertainty Principle used, It's always to talk about how a particles' momentum can only be known to a certain range if it's position is known too precisely, and in problems I've encountered, or vice-versa. In problems I've encountered, often times I'll be asked to find the...

For the ground state of a particle moving freely in a one-dimentional box 0\leqx\leqL with rigid reflecting end-points, the uncertainty product (del x)(del p) is 1 h/2 2 sqrt{2}h 3 >h/2 4 h/sqrt{3} I used (del x)^2 =<x^2>-<x>^2 and (del p)^2 =<p^2>-<p>^2 Using the wavefunction of...

I am having trouble understanding (not for homework) what a wave packet is in terms of the correspondence of the idea of a wave packet to a "point like" particle. I'd like to focus on the 1d wave packet ultimately, but in order to describe my consternation -- let me detour to a well defined...

Why do we use significant figures in calculations instead of the rate of Uncertainty? (2,5\pm0,4000)*4,000=(10\pm1,6). The number 2,5 has 2 significant figures, which is the same as we will write in the answer, while it should be only one significant figure in the answer if we take the rate of...

I think this is right, but could someone confirm (or deny) this for me? While a particle like an electron - or a finite set of particles for that matter - is represented by a single normed vector in Hilbert space which is acted on by operators such as ones for energy, position and momentum...

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...

does the epsilon delta definition of the limit connect to the uncertainty in measurements like this? like if we measure a quantity time with value a with error of + or - delta then my formula will give me v with value L +or - epsilon or is it unrelated?

Homework Statement N=a^+a a=\frac{ip+mwx}{\sqrt{2m\hbar w}} \quad a^+=\frac{-ip+mwx}{\sqrt{2m\hbar w}} |z>=e^{\frac{-|z|^2}{2}}\sum^{\infty}_{n=0}\frac{z^n}{\sqrt{n!}}|n> where <n|n>=1 Show that the variance (uncertainty) in N, \Delta N is |z| i.e. calculate (\Delta...

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...

Homework Statement i have a few results of measurements, with different measurement uncertainty: L=5\pm0,2, L=5,1\pm0,1,L=5,2\pm0,3,L=5,3\pm0,1,L=5,4\pm0,2 and how can i count standard deviation and final result of measurement with uncertainty? The Attempt at a Solution i counted arithmetic...

I was reading the book "the grand design" by stephen hawking and I reached the part about randomness and Heisenberg's uncertainty that I didn't understand. The book seems to suggest that "Probabilities in quantum theories reflect a fundamental randomness in nature". The thing seems right to me...

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.

Hi all, A question about the Holographic Principle. I've recently started reading up about this, and watched Bousso's neat introductory video . I thought, "Ah, this is so refreshingly simple!", and proceeded to write down my own notes. However here things revealed themselves to be not...

Hi, I have just managed to make a PIC light blink. My question has to do with the syntax. In my code, I use a Delay subroutine that is called in between turning the LED on and turning it off. I tried two codes. The first had my Delay subroutine being placed before my main code. The second had...

I'm trying to decide on a method for calculating a weighted mean for my data. In Bevington's Data Reduction and Error Analysis for the Physical Sciences 2nd Ed. Equation 4.19, the variance of the weighted mean is: However, Bevington also suggests the use of Equation 4.22 substituted...

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 will not used the template provided since this is not a textbook problem. It's a problem I have with a demonstration in Quantum Mechanics Vol 1, Cohen-Tannoudji " Complement C III [Q,P] = i \hbar Consider the ket: |\phi \rangle = (Q +i\lambda P)|\psi \rangle where \lambda is an...

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 A metal bar has a length measured to a precision of +-1%, a mass measured to +-2% and a radius masured to +-3%. What would be the % error in the value of the density of the metal in the bar calculated from these? Homework Equations V=(pi)r^2h D=m/v The Attempt at...

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...

Homework Statement I currently want to add 2 percent each with a relative uncertainty together: \frac{53.3\% +/- 1\% + 65.8\% +/- 1\%}{2} I'm not sure how I can add the percentage uncertainty. Homework Equations The Attempt at a Solution I've concluded that the average is...

Hello community. My second stupid question. In the book by Nouredine Zettili , the uncertaintie operators are defined as \DeltaA = A - <A>, where A is an operator, and <A> = <\psi|A|\psi> , with repect to a normalized state vector |\psi> i was wondering, why is not the uncertainty...

In the Messenger Lectures (http://research.microsoft.com/apps/tools/tuva/index.html) Feynman says that the theory of "hidden variables" tells us that the cause of uncertainty in nature (the cause that nature works with probabilities) is that we don't have enough information to predict the...

\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)?

hi, in the position momentum uncertainty principe , should we believe there is an uncertainty about the mass and not only about the velocity? thank you very much for your reply!

After measurements, the following values and their uncertainties were recorded: x = 8.3 ± 0.1 and y = 2.72 ± 0.07 Find the following values of Z a) Z = x + y b) Z = x - y c) Z = xy d) Z = x/y e) Z = y/[(x)^0.5] (this is y divided by the square root of x) f) Z = exp(y)...

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...

From the wikipedia page on http://en.wikipedia.org/wiki/Complementarity_(physics)" : As I recently noticed in the double-slit experiment there is a lot of time-uncertainty, not only position-momentum uncertainty. That is shown in the fact that the probability wave does not reach the screen...

Homework Statement If you were to measure ten identical measurements, would that imply that your measurement of the wavelength had no uncertainty? what would the uncertainty of the measurement be in that case? Homework Equations n/a The Attempt at a Solution I am thinking no...

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...

Homework Statement Consider the points (x, y) = (0,0) and (100,10). Calculate the unit vector u pointing from the first to second. If each coordinate has an uncertainty of +/-2, calculate the uncertainty in u using propagation of error, but making reasonable approximations based on the values...

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

Homework Statement My first lab report in physics requires me to calculate the value of local gravity. I did this using latitude and longitude. I must also state the uncertainty of my local gravity value. I have no clue how to do this. What am I basing my uncertainty on, and is there an...