# Tag Info

### When an electron hits a fluorescent screen mounted on a spring, why can't we get both position and momentum?

If I understand you correctly you have an experimental setup like this. (image partially taken from The Physics of Springs) You measure two things: the $x$ position given by the position where the ...
• 27.6k
Accepted

### What relationship, if any, exists between Heisenberg's uncertainty principle and this general principle of uncertainty?

3B1B's Youtube video mainly talks about the Fourier uncertainty principle between a function $\psi(x)$ in position space and its Fourier transform $\hat\psi(\xi)$ where $\xi$ is the spatial frequency ...
• 27.6k

### What happens when a laser beam is stuck between two mirrors and the distance in-between is decreased gradually? Heisenberg Uncertainty Principle

I will add yet another answer, which would be the most accurate to your description of a laser beam bouncing between 2 mirrors (if starting from "macro" distances), albeit my lack of time ...
• 1,018
Accepted

### Can Heisenberg's uncertainty principle be used to prove the electron can't exist in the nucleus in this way?

It’s a mistake to invoke relativity on the speed $v$ without also using the relativistic momentum $p$. But if this is a text for students who may be a little weak on relativity, it’s perhaps a ...
• 74.3k

### Does this video from Veritasium imply that the uncertainty principle is false?

No, the video does not imply that the uncertainty principle is false. But it does imply that you have to be careful/precise to claim what the uncertainty principle is about. It is actually a claim ...
• 7,781

### What relationship, if any, exists between Heisenberg's uncertainty principle and this general principle of uncertainty?

It is very easy to be seduced by the analogy between Fourier pairs like $x$ and $p$ and the HUR but the relation is basically coincidental. It is true that $x$ and $p$ satisfy Fourier-type relations ...
• 39.5k

### Does uncertainty principle apply to holes/gaps in matter?

Holes in semiconductors move as electrons do, but act as if they were positively charged particles. The question really is, are quasiparticles, with an electron "hole" being one type, ...
• 25.6k
Accepted

### Why Heisenberg's Uncertainty Principle?

There are laws that allow the energy transfer between EM radiation and charged particles to be predicted when they collide; but it yields probabilities applicable to large numbers of interactions ...
• 75.1k

### Does uncertainty principle apply to holes/gaps in matter?

Yes, the uncertainty principle does apply to holes/gaps in matter. The uncertainty principle between position and momentum is very general. It follows from the fact that the observable we call ...
• 51.4k
Accepted

### Do the mean lifetimes of short-lived particles follow a Gaussian (or 'normal', or 'standard') distribution? When plotted?

Yes, indeed, the average lifetime will tend to the normal distribution, as required by the Central limit theorem. A caveat: one has to distinguish between the distribution of lifetime and the ...
• 40.8k

### What happens when a laser beam is stuck between two mirrors and the distance in-between is decreased gradually? Heisenberg Uncertainty Principle

A similar experiment is what I call quantum fly. The classical fly problem is well known: From point A and point B two trains depart simultaneously towards each other along the same track with speeds ...
• 40.8k

### Can Heisenberg's uncertainty principle be used to prove the electron can't exist in the nucleus in this way?

The solution given here is wrong. It uses the non-relativistic expression for momentum, and then compares the velocity with the speed of light, which is the velocity limit of relativistic mechanics. ...
• 26.7k

### What happens when a laser beam is stuck between two mirrors and the distance in-between is decreased gradually? Heisenberg Uncertainty Principle

Note: the following was intended as a response to a question posed in the comments of a previous answer ("why does the force increase as we move the mirrors together?"), not as a complete ...
• 9,164
It would be far simpler to just directly measure $x$ of your first beam and $p_x$ of the second beam. Both of which, $x$ and $p_x$ can be measured to arbitrary precision thus violating the ...