Uncertainty Definition and 1000 Threads

If I understand things correctly, the coherent state of a laser beam implies that the photon quantum field is a superposition of states with different particle numbers. This also implies that a laser beam is not in an energy eigenstate. To get energy conservation, I assume that this...

I'm given a form of Heisenberg's uncertainty principle in the form of: \Delta E\Delta t\geq h I need to determine a time interval which would allow a laser to cover the whole visible spectrum, from 400 to 700nm. Now given the relationship is on on a relative scale I used the approximation...

i've seen both: ΔxΔp >= h/2 and ΔxΔp >= hbar/ 2 used, and I'm not sure which is correct. my physics textbook uses h/2, but wiki and other online rescources seem to use hbar/2 do they apply to different situations? (if so, where do you use hbar and where do you use h?) or is one...

WHat is the uncertainty in a metre rule?? For a single value is it 1 mm or is it 1/2mm(half the smallest division) ? And what about measuring something like a length of a stick (we need to take 2 readings, and deduct them like 15-0=15), then is the uncertainty 1+1=2mm or is it .5+.5=1mm ?

Homework Statement The position and momentum of a 1.00 KeV electron are simultaneously determined. If the position is located to within 0.100 nm, what is the percentage of uncertainty in its momentum? (Arthur Beiser - Concepts of modern Physics, 3rd Part exercise 33)Homework Equations...

Hi, This is actually related to my research work. Let say a location (x1,y1) is given with uncertainty in location is given by co-variance matrix P1. A vehicle is moving towards (x1,y1) from a location (x2,y2) with velocity (x2dot, y2dot). The uncertainty of the vehicle location is given by...

Homework Statement I'm looking for graphs or other sources of uncertainty principle visualization (I'm suppose to use a Fourier transform to solve it and present visualization in MS Excel... but one thing at a time). Homework Equations The Attempt at a Solution Digged google in 3 languages. I...

Ok so my textbook explains all the rules to carry the inherent uncertainty in measurements through mathematic calculations (the result of an addition must have as many decimal places as the term with the least decimal places, etc, it also explains significant figures etc...) and at the very end...

My group messed this experiment up and now i have to get a good grade(i receive 50% on all of my labs!). I would highly appreciate your input. Our teacher gave us a procedure sheet, which we "accurate followed" This is what we did:(If this is not enough i have a few more steps that were done...

Homework Statement Assume speed of 435g football is known with 1mm/s uncertainty. What is the minimum uncertainty in its position? Homework Equations I'm not quite sure... I know p=mv, and I know that Heisenberg's uncertainty principle states that certain parameters of quantum...

Homework Statement When a mass of 166.5 ± 3.0 g is added to a spring the spring extends 7.20 ± 0.16 cm. What is the uncertainty in the spring constant, k? You may assume g is known precisely with no uncertainty. Homework Equations The Attempt at a Solution I just converted...

hi i have some measured values that refer to a simple experiment where a stone was thrown along a fixed length and now i have these values for the time the stone needed time 13.8 13.7 13.9 13.5 14.4 14.6 14.1 14.3 13.9 14.7 i was asked to explain how many decimal places one would write...

What is the uncertainty speed of a hydrogen atom inside a virus? Even though the vaue of uncertainty in position is not given. Any help on this would be greatly appreciated. Thanks!

How do we know that the uncertainty principle is a property of an electron and not a limit of our measuring ability? I understand that photons striking an electron alter its momentum, but imagine an electron that is not being observed. Couldn't it have both a position and a momentum at a given...

Hi, I'm working on a homework for my solid state physics class and I'm having trouble with this question: Homework Statement "We have seen many cases in solid state physics in which you can apply the concept of uncertainty principle to estimate some quantity. Describe two examples of a...

Hello...sorry about the vague nature of the question..but I am trying to learn in an 'economical' sort of way. That is asking almost redundant questions..but answers I can work with in a 'free style' way...and gain understanding in the process or be able to ask another question. Can someone...

http://quantummechanics.ucsd.edu/ph130a/130_notes/node98.html Can someone help me understand what's going on here? He says "The idea is that the radius must be larger than the spread in position, and the momentum must be larger than the spread in momentum." which I suppose must be true in...

Heisenburg Uncertainty Principle - Seems like an easy question?? Homework Statement The position of a 900 kg boulder's center of mass has been determined to within an uncertainty of 1.0 nm. (a) What is the minimum uncertainty in the boulder's velocity? (b) Repeat the calculation, but for a...

According to the De Broglie-Bohm theory, is the universe, in its current state, the only one that could have evolved from its early conditions? In other words, because in the theory, each particle actually possesses well-defined position/momentum/trajectory, does the theory imply that the...

i tried to apply uncertainty principle to an electron confined in a 3d box of size 1fm. i got uncertainty in velocity Δv to be of the order 1010 m/sec.so i thought maybe i should have taken relativistic mass instead of rest mass. but i realized that for calculating relativistic mass we...

Homework Statement I cannot work out how to calculate my percentage uncertainty for my coursework, i need to show that my second method has a reduced uncertainty than my first, could anybody please enlighten me as to how to work it out. My table for one of the practicals is attached Homework...

Let us assume that harmonic oscilator has the lowest energy level equals 0, (and next one \hbar \omega and so on). Does this harmonic oscilator violates the principle of uncertainty? Let us assume that energy of vacuum equals 0 and not \hbar \omega/2. Does such vacuum violates the principle...

Can somebody please explain the basis for the Heiseinberg's Uncertainty Principle and the Schrodinger's Theory or me? I m confused with the movement of electron in the orbitals and i think these 2 theories are the key. Thanks

I had a quick question on the uncertainty principle. I'm not a physicist but I'm familiar with the basic theories. I've never had anyone explain it to me like this, but this seems to be an intuitive way to look at it. So I need to know if I'm framing this right. In classical, you start...

Can anybody clear this up for me? In his Chicago lectures in 1930, Heisenberg is quoted as saying “The uncertainty relation does not hold for the past…If the velocity of the electron is at first known, and the position then exactly measured, the position of the electron for times previous...

[L_x,L_y]=i \hbar L_z \neq 0. In fact it seems we can know only the modulus squared of the angular momentum and one component, at a same time. However if I take an electron say in the fundamental state in the hydrogen atom, L=0. Since the modulus squared is equal to 0, it means that all...

Hi guys, So I'm writing up a physics lab and I have a bunch of data points. All of these data points have both x and y error bars. The relationship between x and y is linear and so I've made a line of best fit using Python passing through the data. Now the slope of that line of best fit...

The general definition is that we cannot determine the location and velocity of a particle at any given moment. However, my intuition is to assume this is due to shortcomings in technology and measurement, but apparently that's false. This is a rule of nature. Can you explain what exactly the...

Let’s say I have a class A 25ml pipet with an uncertainty of +/- 0.24ml. If I want to express the volume of the pipet to the correct number of sig figs to say determine the sig figs in a final answer - what is it? Is it 25 ie two, because that is the marking? Or 25.00 ie four...

Homework Statement A laser produces light of wavelength 540 nm in an ultrashort pulse. What is the minimum duration of the pulse if the minimum uncertainty in the energy of the photons is 1.0%? Homework Equations ΔEΔt ≥ hbar / 2 The Attempt at a Solution Now I tried a couple ways...

Uncertainty values for non-Gaussian wave packet functions Homework Statement \phi(k)= \left\{ \begin{array}{cc} \sqrt{\frac{3}{2a^3}}(a-|k|), & |k| \leq a \\ 0, & |k|>a \end{array} \right. \psi(x)= \frac{4}{x^2}sin^2 (\frac{ax}{2}) Calculate the uncertainties \Delta x and \Delta p and check...

Homework Statement I have conducted an experiment and found the gradient λ of a graph to be (2.15x10^-4) +- (0.15x10^-4) The graph being ln(A) i.e. the number of disintegrations/unit time - dN/dt against time t The half-life is T(1/2) = ln(2)/λ = -3223.9 How do I find the...

Homework Statement Suppose that at one instant in time the wavefunction of a particle is ψ(x) = \sqrt{b}e-b|x| Estimate the uncertainty of Δx for this wavefunction. Homework Equations ΔxΔp ≥ h(bar)/2 h(bar) = h/2pi The Attempt at a Solution Do I just calculate the...

I don't understand how to calculate percentage uncertainty!? I know in chem we calculate uncertainties by smallest division/the reading X 100. But in physics i am clueless. For instance here's an example The power loss P in a resistor is calculated using the formula P = V^2/R. The...

When I read about the uncertainty principle, I keep reading about these experiments where they fire electrons through a single or double slit and observe the diffraction but I can't these experiments relate to Heisenbergs uncertainty principle. So when they fire the electrons, they know their...

I have seen an argument that the time-energy uncertainty relation allows heavy particles to exist for short periods of time as virtual particles: (ΔE Δt)>h Δt>h/ΔE However, shouldn't the inequality be the other way: Δt<h/ΔE to suggest that a heavy particle with large ΔE can exist...

Homework Statement Check the energy-time uncertainty principle for: \Psi(x,0)=Ae^{-ax^2}e^{ilx} using the observable x. Homework Equations \Delta{E}\Delta{t}\geq\hbar/2\\ \Delta{E}=\sigma_H=\sqrt{<H^2>-<H>^2}\\ \Delta{t}=\frac{\sigma_x}{\frac{d<x>}{dt}} The Attempt at a...

Homework Statement Consider the nonstationary state: \Psi = \sqrt{\frac{1}{3}}\Psi_{22-1} + \sqrt{\frac{2}{3}}\Psi_{110} Where \Psi_{22-1} and \Psi_{110} are normalized, orthogonal and stationary states of some radial potential. Is \Psi properly normalized? Calculate the expectation value of...

Hello my teacher said that percentage uncertainty is a measure of precision and percentage difference a measure of accuracy. i thought it's the other way round?? say if i have 20% and 80% what do these values tell me in terms of precision and accuracy?

Homework Statement I am doing percent difference of 2 values. value 1 = .013329 +- .001 cm value 2 = .013331 +- .001 cm So, for percent difference I do: .013331 - .013329 / ((.013331 + .013329)/2) gives me .015%, but what would my uncertainty be? I don't wuite understand...

Homework Statement If the uncertainty in the location of a nonrelativistic particle is about equal to twice its de-Broglie wavelength, show that the uncertainty in its velocity is greater than about 4% of its velocity. Homework Equations ΔpΔx>h/4Pi p=mv Δx=2nλ The Attempt at a...

1. Homework Statement The figure shows 1.0*10^-6 m diameter dust particles in a vacuum chamber. The dust particles are released from rest above a 1.0*10^-6 m diameter hole, fall through the hole (there's just barely room for the particles to go through), and land on a detector at distance d...

Homework Statement The figure shows 1.0*10^-6 m diameter dust particles in a vacuum chamber. The dust particles are released from rest above a 1.0*10^-6 m diameter hole, fall through the hole (there's just barely room for the particles to go through), and land on a detector at distance d...

Derive the relation Δn.Δσ ≥ 1/2 where n is number of photons in an EM field and σ is phase Using heisenburgs uncetertainty principle? Tried subbing in frequency into heisenburgs uncertainty principle to get to the number of photons and to get rid of mometum is this the right line? Dont...

As you know,a pure sine wave extends infinitely in both directions and a wave which is the composition of some different frequencies,has a limited extent.Does it mean that such a wave is a pulse moving in space or it has limited range?(I know its crazy to talk about the range of light,but I've...

In a lab, i used a micro-caliper to measure the diameter of an indicator; I got 3.681 mm \pm 0.005 mm. However, i need the measurement to be in meters and i need to divide the measurement by 2 (as i need the radius, not diameter) for easy calculations. I know how to convert the 3.681 mm to...

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...

Homework Statement "You are asked to do an experiment where you will need to use a rotating blade to measure the wind speed. You measure the number of rotations of the blade at 10 different wind speeds, 10 times each and will make a linear fit to determine the wind speed as a function of...

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?

Physics Uncertainty Question? Homework Statement I have Vy = 0.125tan(54) = 0.17204. I have to find the uncertainty of Vy Where 0.125 = A and tan(54) = B uncertainty of A (0.125) = 0.0005 uncertainty of B (54 degrees) = 0.5degrees Homework Equations Uncertainty for Multiplication =...