uncertainity principle

1. How can I calculate the smallest speed of a proton in a nucleus?

My approach: Assuming non-relativistic velocity: $$p = mv$$ $$mvL = \frac{\bar{h}}{2}$$ $$v = \frac{\bar{h}}{2mL} = \frac{h}{4\pi mL}$$ $$v = (6.626*10^-34) / (4pi * 1.67*10^-27 * 4.3*10^-15)$$ $$v = 7.34*10^6 = .0245c$$ This answer is incorrect. What have I done wrong? --- Edit: My...
2. How to get the Uncertainty of a percentage change

I have a measurement with uncertainties for two years. Say Year 1 Rain : 100mm(80-120mm) Year 2 Rain : 120mm(103-131mm). Now I get the percentage change in rain in Year 2 w.r.t Year 1 as 20%. Is there a way to get the uncertainty associated with this percentage change?
3. A Resolving power of a radio telescope array: Quantum or classical?

My question is: is the resolving power of an array of radio telescopes a quantum or a classical effect? The increase in resolving power of a single telescope, as aperture size increases, is easy to explain in terms of Heisenberg's uncertainty principle. But when we go an array of telescopes are...
4. Uncertainty product

1. Homework Statement For the ground state of a particle moving freely in a one-dimensional box 0≤x≤L with rigid reflecting end points, the uncertainity product (Δx)(Δp) is (A) h/2 (B) h√2 (C) >h/2 (D) h/√3 2. Homework Equations The uncertainity principle says that - (Δx)(Δp) ≥ ħ/2 Ground...
5. I Heisenberg - Uncertainty principle - lifetime of a particle

I have seen that the more a particle has a high energy, i.e $E$, the more its lifetime is short, respecting so the uncertainty principle. But by the definition of this uncertainty principle : $E\,\Delta t \geq \dfrac{\hbar}{2}$, I can write : $\Delta t \geq \dfrac{\hbar}{2E}$, then...
6. I What's the significance of HUP if Ψ collapses?

If I understand it correctly, a particle doesn't have a definite momentum and a definite position, but is in a superposition of multiple positions and momenta. And when we measure either of the two quantities, say, position, the wavefunction collapses to tell us where the particle is. Now when...
7. I Why is the Uncertainty principle inherent to particles?

If we have a particle, say, an electron and we shoot it straight through an empty box. This box is surrounded by light sources on its two sides: So, if you consider the above cube, if we shoot a particle in a straight line such that it crosses the face ABEF and it crosses the face HGDC through...
8. I Are the energy fluctuations in space real or virtual?

Heisenberg's uncertainty relation says: $$\Delta x \Delta p \ge \hbar$$ If we assume a massless quantum object then we have the relationship $\Delta E = c\Delta p$ so that the above uncertainty relationship becomes $$\Delta E \ge \frac{\hbar c}{\Delta x}.\tag{1}$$ I understand that if we have...
9. I Finite universe, quantized linear momentum, and the HUP...

Hi all, Yet another question: if the universe is finite, then linear momentum should be quantized (I assume in a similar manner to an infinite potential well since there are boundary conditions). My question is, then, if one computes a value for $\Delta p$ (momentum variance), is the variance...
10. I What is the origin of Van der Waals force?

Hello. What I know about the Van der Waals force is that it comes from an instantaneous electronic cloud flucutation of the netural atom. This instantaneous electric dipole of the atom attracts electrons in nearby neutral atoms so other electric dipoles are induced on those atoms. As a result...
11. A Uncertainty paradox?

Imagine a spatial frame of reference attached to a point-like particle. It has x=0 since it is at the origin and p=0 since it is at rest. Having definite position and momentum is normally considered a violation of the uncertainty principle. How would you resolve this paradox? 1. Position frames...
12. B Are vertical lines from squinting a Quantum phenomenon?

When looking at a night light with almost closed eyes, I notice that the light becomes a vertical line. When tilting my head 90 degrees, the line becomes horizontal. Can this be explained by Heisenberg's Uncertainty principle? This question has been asked in another thread : "Squinting at...
13. Single slit with minimum uncertainty

1. Homework Statement A horizontal beam of laser light of wavelength 474 nm passes through a narrow slit that has width 5.80×10−2 mm . The intensity of the light is measured on a vertical screen that is 2.40 m from the slit. Use the result of part A to estimate the width of the central...
14. J/psi meson detection

1. Homework Statement See Image The bit about Spectral lines, I couldn't explain why 2. Homework Equations ΔEΔt≈h 3. The Attempt at a Solution I expected the histogram to peak at the given mass in question and to have a width of about 0.08 MeV calculated as ΔE from the Energy-time...
15. I Uncertainty of frequency

what can be the uncertainty of the frequency that humans can hear ? I'm aware that there are many ways,but i tried google-ing to find them but i couldnt. if you could help me it would be great.
16. Determinism and Uncertainity Principle

Dear PF Forum, Determinism. 1. Is there determinism? 2. Because we can't measure the electron position, it doesn't mean there's no determinism? Heisenberg uncertainity principle states, per wiki: But because we can't measure it, it doesn't mean that the universe itself is indeterministic...
17. How is the uncertainty relation preserved in this experiment

For an electron can I not do the following to determine both the position and momentum? I take a screen with a small hole and I eventually make the hole smaller and smaller. Cathode rays emitted will hence get diffracted after passing through the hole making momentum more and more uncertain...
18. Is this statement about the Uncertainty Principle correct?

I was reading the Feynman Lectures awhile back and I remember reading something he said about the Uncertainty Principle and it seemed slightly odd to me. I don't remember the exact quote and combing through some of the lectures online I can't quite find it. I've heard it more than once from...
19. Uncertainity Principle: possible to know the momentum and position?

The principle states it is impossible to 'simultaneously' know the position and momentum(velocity)of an object. Position is something that can be noted at a particular instant, as from a photograph whereas velocity is something that can only be measured over a period of time,as from a movie. The...