Uncertainty Definition and 1000 Threads

Homework Statement Calculate the following, expressing all results with uncertainties both in absolute and relative (percentage) form: a) A + B b) A x B c) Asin(theta) d) A^2 / Bcos(theta) The relevant formula for the absolute uncertainty is below, but i have no idea how to...

Hi, I have taken an introductory undergraduate QM course, solving for different boundary conditions like particle in a box, but the physical interpretations of some of the tenets was not well explained. I was surprised to find this paragraph on Wikipedia: "Published by Werner Heisenberg in...

Homework Statement The radius of a circle is measured to be 14.3+-0.3cm. Find the circle's area and the uncertainty in the area. I don't understand how to correctly apply uncertainty equations with sigma and partial derivatives to these types of problems. Homework Equations...

Homework Statement Show that the smallest possible uncertainty in the position of an electron whose speed is given by \beta = v/c is \Delta x_{min} = \frac{h}{4 \pi m_0 c}\sqrt{1-\beta^2} The Attempt at a Solution Since \Delta x \Delta p \geq \frac{\hbar}{2} , we see that \Delta x_{min}...

Does the uncertainty principle apply only to electrons or other particles as well?

Hello everyone. I need your help. I am not a physicist or a physics student, so I am not familiar with the subtleties of quantum mechanics. I do have a good general education, though, and I am eager to learn new things. I have long had a problem with quantum mechanics, specifically the...

Hi, I am trying to teach myself some quantum mechanics and here is something I am stuck on. Various derivations of Heisenberg uncertainty start out with two Hermitian operators, usually called A and B to represent position and momentum. Then they define another two operators ∆A and ∆B as...

Hi people. I am a bit confused about the uncertainty principle. According to Heisenberg, we cannot exactly determine the position and momentum of an electron at the same time because the minimum energy we have to give out (say light energy) is absorbed by the electron and one of the quantities...

I am a little confused by something by something in my physical chemistry textbook. If two measurable quantities do not commute, then an uncertainty relation exists for them. Kinetic energy and position do not commute, and the expectation value for linear momentum in a 1-D particle in a box...

1. this is for a particle in a box (infinite potential well): For the wave functions calculate (as a function of n) \Deltax \Deltap \Deltax\Deltap Homework Equations h = h bar below u+n(x)=(1/\sqrt{a} )cos((n-1/2)(pi)x/a) u-n(x)=(1/sqrt{a})sin(n(pi)x/a) E-n=h2/(2m)(n(pi)/a)2...

A particle is confined within a spherical radius of one femtometer(10^-15 m)? Its momentum can be expected to be about- 1. 20 keV/c 2. 200 keV/c 3. 200 MeV/c 4. 2 GeV/c How should I go about using HUP on a problem like this one? I tried substituting x=10^-15 meters in px=h/4 pi but the answer...

Homework Statement How do we solve this problem? % Difference = (l 0.282 +/- 0.0019 - 0.288 +/- 0.04 l) / 0.285 +/- 0.02 Homework Equations Percent Difference = (l value - average value l)...

First, I'm not sure where this fits (here or Quantum Mechanics), because it's completely in-between the two... Is there a way to account for the fundamental uncertainty in quantum mechanics through a modification of general relativity? I have very limited experience in Quantum mechanics, and...

I have a quite simple doubt. One of the practical applications of Heisenberg's uncertainty principle is given by Heisenberg's microscope. In this thought expt. Heisenberg imagines of a hypothetical microscope in which an observer attempts to measure the position and momentum of an electron...

Homework Statement Determine the percent uncertainty in theta and in sin theta when theta equals 20.0 + or - 0.5 degrees? delta theta/theta = ? delta sin theta/ sin theta = ? Homework Equations Percent uncertainty is a ratio of the uncertainty to the measured value. %uncertainty =...

Hello, I have done a chi squared test on the measurements from a neutron flux experiment to get the best parameters for a function of the form Ysim=Acos(B*X). I used Solver in Excel to find the minimum parameters. The test takes the form chi^2 / dof = SUM(Ysim-Yi)^2/(sigma i)^2 Where...

hi, I have a question about the uncertainty principle. if an electron is in attractive OR repulsive electromagnetic field, is its uncertainty about its position lower than if it is a free electron? I believe particles are more random, with a higher entropy when there is less...

Homework Statement [PLAIN]http://img137.imageshack.us/img137/4242/probhr.jpg Well ,my problem is why after substitution for the first time the result os uncertainity (0/0) Is X=0? and I don't understand the step no 2

Uncertainty for a ratio (urgent help!) Question: As you eat your way through a bag of chocolate chip cookies, you observe that each cookie is a circular disk with a diameter of d = 8.32 cm +/-1×10−2 cm and a thickness of h = 9.3×10−2 cm +/-1×10−3 cm. Find the uncertainty in this ratio of the...

I was reading about this, but I'm unclear on something. Does the Heisenberg principle arise due to limitations in technology? Or is it an absolute physical phenomena that can't be avoided no matter how advanced your measuring tools are?

I've been trying to understand the uncertainty principle and so far the Wikipedia definition has been very good explainig position and momentum relationship, but the aperture size explanation below is beyond me. Any help? "If a large aperture is used for the microscope, the electron's...

I am having a lot pf problem to attempt this question, please help me, i am stuck..! The power loss P in a resistor is calculated using the formula p=v^2/R The uncertainty in the potential difference V is 3% and the uncertainty in the resistance R is 2%. What is the Uncertainty in P...

Homework Statement hi i am new to this principle if i was to calculate the Heisenberg uncertainty of a nuclei of radius r would i take my delta x as r or as the diameter of the nuclei thanks Homework Equations The Attempt at a Solution

I hope a pointer to a speculative post on a blog is OK in this group. But as the posting rules at https://www.physicsforums.com/showthread.php?t=5374 reference a dead page, I was unable to check ;-) (It would be easy to copy and paste that article here, if that is considered desirable to...

Homework Statement A semi-conducting thermistor has a resistance that veries with temperature as follows: R(T)=R_0 exp[\frac{B}{T}] What are the SI units of the calibration constants B and R_0 This is just the intro chapter to my second thermodynamics course. Anyway, I'm not sure how to...

There is something (among many things of course) that confuses me with the uncertainty principle as it pertains to position and momentum of a photon. If one shoots a photon of red light, for example, at a screen, one can see where exactly the photon hits the screen so position is known. Also...

Homework Statement this isn't really a word problem, it's part of a series of calculations from a physics lab in this lab, Ug = energy at initial position Ug -> Ekrot + Ek at final position I need to calculate 1. Ekrot 2. Moment of Inertia 3. angular velocityHomework Equations Ug = mgh...

I appologize if my questions make no sense (very likely as I do not have a physics background). 1. The uncertainty principle states that precision of measurement is identified only down to the Planck's constant. If this is so, how can one measure the speed of light with infinite precision? ANd...

If we've perfectly located all of that mass, doesn't its momentum have to be infinetly or maximally dispersed. It would be a slow motion big bang from our frame because of space and time contraction and we couldn't even see it, but it seems like the mass should disperse in some diffraction pattern.

are there any theories right know to solve it

Based on the results of every variation of the two-slit experiment so far, the presence or absence of the interference pattern is based on whether or not which-path information can be known or not. The Delayed Choice Quantum Eraser experiment...

I have read some books about quantum physics.There are about too kinds of interpretation about uncertainty relationship.The first is that it consists in single measurement.However the other one is statistical explanation that it just consists in measuring repeatedly.I support the former...

Homework Statement Let's say T is kinetic energy and V is Potential. Then, find a principle between T and V by using dA^2dB^2 (larger or equal) {(1/2i)(<[A,B]>)}^2 3. The Attempt at a Solution First I try to find commutator of T and V, [T,V] then it gives little bit dirty...

I've been following Peter Lynds work- which is a periodic rediscovery of the philosophical difficulties surrounding the concept of discontinuity, threshold, edge etc and its application to Zeno's paradox. Lynds' solution has emerged a number of times in showing the paradox is invalid because...

Homework Statement Estimate the kinetic energy of a constituent quark of mass 300 MeV/c^2 confined insdide a proton of radius 1 fm Homework Equations Heisenberg's uncertainty principle \Delta x \Delta p \approx \hbar (1) Kinetic energy T=\frac{p^2}{2m} (2) The Attempt at a...

Uncertainty Principle Questions!PLease HELP! Homework Statement 1. Since a charged pi meson at rest exists on average for only 26 ns, its energy cannot be measured with unlimited precision. Determine the minimum uncertainty in the meson's rest energy. 2. Determine the minimum uncertainty in...

We have the uncertainty principle. How would our world be different, if someone measured position and momentum of a particle with 100% accuracy? Would some other laws of physics be violated, too? I mean - what laws of physics depend on uncertainty? It is clear to me, that the whole...

From what I understand, the Heisenberg Uncertainty Principle means that we can never know the position and velocity of a particle at the same time, as the measurement of one necessarily affects the measurement of the other. Great. I understand that theory, and it makes perfect sense. But what...

Homework Statement I am trying to understand how we go about calculating the density of states in situations where the available quantum states are continuous, e.g. electrons in a white dwarf. I am happy to accept the uncertainty relation (we learned to derive it as the product of the...

I would like to know if the electric charge of a particle, like electron, has always a definite value, or on the contrary the Heisenberg uncertainty principle should be applied to this magnitude. Or asking that in another way, what is the observable operator associated to the charge of a...

Homework Statement Find the equivalent resistance viewed by A and B and its equivalent uncertainty: http://img707.imageshack.us/img707/5040/dadadadaz.png R1 = 10ohm, 5% tolerance. R2 = 2ohm, 1% tolerance. R3 = 5ohm, 5% tolerance. R4 = 15ohm, 1% tolerance. The Attempt at a Solution...

Homework Statement V=\pi r^{2} h The uncertainties in V and h are shown below V 7% h 3% The approximate uncertainty in r is: A. 10% B. 5% C. 4% D. 2% 2. The attempt at a solution According to the key the correct answer is B. This answer can be calculated by: r^{2}=\frac{V}{\pi h} which...

I got in an argument with my dad over the weekend. Is the Heisenberg uncertainty principle a result of technological limitation or a basic premise in quantum mechanics? Basically is the information fundamentally "unknowable" or simply unmeasurable?

In non-relativistic wave mechanics, the momentum-position uncertainty relationship and the energy-time relationship exist because these variables are related via the Fourier Transform of the wave function. Is there a relativistic (QFT) equivalent or analog of the above px and Et uncertainty...

what is uncertainty principle? thanks ppl..

i have two questions that i am struggling with and i have tried all i can think of with them and i am still not getting the answers correct. 1)Estimate, using the Uncertainty Principle, the kinetic energy of an electron if it were bound in the nucleus. Answer: ∼ 200 MeV for R ∼ 1 fm...

Sorry if this question has already been asked many times, but I found no answer after a quick search. Have already made an experimental test of the Heisenberg's inequalities: \Delta p \Delta x \geq \hbar I'm quite sure our instruments' imprecision are larger than Planck's constant, but I...

Homework Statement A small flat circular disc of diameter 2mm and mass 5mg is lowered vertically to rest at the centre of a flat tray of width 10mm in the x direction and 50mm in the y direction. What is the minimum uncertainty in measuring the velocity of the particle in the x direction...

Homework Statement 1) I try to understand the lorentzian lineshape and relate to the gaussian graph but i don't know what is the difference. 2) Uncertainty principle- if it's related to the lorentzian lineshape it will give the information about the lifetime in the well and the width of...

I was reading about how Heisenberg found out that it is "impossible to determine simultaneously with unlimited precision the position and momentum of a particle" (Serway/Moss/Moyer, 174) \Delta p\Delta x \geqh/2 (where h is plank's constant over 2pi.) My question is why is this true? I...