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Questions tagged [experimental-physics]

For questions about design, process, data, or analysis of experiments and observations.

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What evidence do we have for GR in the nonlinear regime?

The classical equations for Einstein's GR (modulo the cosmological constant) read $$R_{\mu\nu} - \frac{1}{2} R g_{\mu\nu} = \kappa T_{\mu\nu}.$$ These equations have a complicated linearization that ...
Panopticon's user avatar
1 vote
0 answers
15 views

How does MEMS low insertion loss fiber optic switch work? [closed]

I'm currently looking for a low insertion loss fiber optic switch to be able to change the light source of a spectrometer. Since this will be used in harsh conditions, I was hoping to find one with no ...
coffee's user avatar
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0 votes
1 answer
21 views

Why were multiple layers of absorbers and scintillators used in the CMS HCAL?

Why were multiple layers of absorbers and scintillators used in the CMS HCAL? Couldn't they have used just one absorber and one scintillator layer? Why was the choice made to have multiple layers?
secondquark's user avatar
0 votes
0 answers
122 views

Suspiciously wrong value by factor of $1/2$ in experiment to calculate frequency of AC mains using sonometer

In school we performed the following experiment: We use a step down transformer ($220V$ to $6V$) and pass current through a "sonometer wire". We have a meter scale underneath the wire. ...
AVS's user avatar
  • 324
3 votes
2 answers
1k views

Foucault's measurements of the speed of light

I understand that you can — in principle — measure the speed of light with the rotating mirror experiment. What I don't understand: How can you accurately measure (or fix) the number of rotations of ...
J Fabian Meier's user avatar
5 votes
3 answers
637 views

Half wave plate + polarizer vs rotatable polarizer + fixed polarizer

I am learning about optical setups and am looking at how the intensity of the laser beam is attenuated for use. A lab in my institute uses a rotatable Half Wave plate and a polarizer fixed at the ...
physicmystique's user avatar
0 votes
1 answer
140 views

What is the actual version (using electrons) of this quantum thought-experiment from an MIT lecture?

In the first lecture of the MIT quantum-mechanics 2013 course, the professor develops basic abstract concepts, by inventing hypothetical binary measurable properties of electrons (hardness (H)= hard ...
Terminality's user avatar
1 vote
0 answers
43 views

What's the theoretical max output of the National Ignition Facility (NIF)?

With the latest Ignition event at the National Ignition Facility (NIF) producing 3.5Mj of energy, I'm curious to know. Using the pellets that they are, what's the maximum energy they could produce, ...
TechPlasma's user avatar
0 votes
1 answer
227 views

How to measure the tension in a guitar string without directly measuring the frequency of the sound?

I'm looking for an accurate method to measure the tension in a guitar string, without using a sonometer setup nor by measuring the frequency. the current method that I have in mind is to measure the ...
Kian's user avatar
  • 1
6 votes
2 answers
258 views

Specific experiments that affirm particle-in-a-box QM theory

The infinite square well (and variations) are some of the best-studied systems in quantum mechanics and are often used as the starting point for any quantum mechanical education, as the Schrodinger ...
YaGoi Root's user avatar
0 votes
1 answer
83 views

Has Quantum Spin of a Single Particle Been Measured Twice Experimentally?

In quantum mechanics, the concept of spin is fascinating. My question revolves around the experimental aspect of this phenomenon. Specifically, I'm curious to know if we have ever measured the quantum ...
realFishSam's user avatar
0 votes
0 answers
21 views

What are the two basic experiments to identify different phases in high $T_c$ cuprates systems?

what are the two basic experiments to identify different phases like antiferromagnetic, pseudogap, superconducting, strange metal and fermi-liquid in high $T_c$ cuprates systems like BSCCO and YBCO?
Rick Andy's user avatar
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1 vote
0 answers
56 views

SLM pulse shaping to delay (and advance) ultrashort pulses in time

I am trying to replicate some of the experiments discussed in this excellent publication: SLM for pulse shaping In particular, I replicated the setup configuration in Figure 14 and I want to use the ...
France's user avatar
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1 vote
0 answers
122 views

How we know that Dirac equation in curved spacetime is the correct one?

Dirac equation in curved spacetime is given by $$\left(i \gamma^\mu D_\mu-m\right) \Psi=0$$ How does we know that this is the correct equations to describe spinors in curved space time? Is there any ...
amilton moreira's user avatar
1 vote
1 answer
67 views

Is there an intuitional way to tell which physical quantities are angular frequency and which are frequency?

Such as the natural linewidth is defined to be angular frequency, while the absolute frequency of laser is frequency. By far I haven't found a good way not to learn it by roting. Would anyone be ...
QubitTy's user avatar
  • 31
2 votes
3 answers
37 views

Probability distributions of bounded measurement results?

Say that I am measuring a length very inaccurately. For instance, I might measure $1m$ with an uncertainty of $50cm$. If I model the probability distribution as a Gaussian with $\sigma=50cm$, I run ...
dknapp's user avatar
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2 votes
1 answer
287 views

Up-to-date values of Yukawa couplings (2023)

Where can I find the most recent values for the Yukawa couplings in 2023? I currently have access to the values from 2011, but I guess precision has improved over the last decade in measurements. Edit:...
Manuel's user avatar
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1 vote
0 answers
33 views

Cloud Chamber Help Needed! [closed]

I was inspired by this video to attempt to create a cloud chamber without dry ice (it's very challenging to get where I live) and I have had limited success so far. This is what the design looks like: ...
Carl Davis's user avatar
0 votes
1 answer
97 views

Why aren't the Standard Model predictions of $R(D)$ and $R(D^\ast)$ equal to 1?

The observables $R_K$ and $R_{K^\ast}$ are defined as $$R_{K,K^*}(q_a^2, q_b^2) = \frac{\int_{q_a^2}^{q_b^2} \frac{d \Gamma (B^{(+,0)} \rightarrow K^{(+, \ast 0)} \mu^+ \mu^- )}{dq^2} dq^2}{\int_{q_a^...
jmaguire's user avatar
  • 313
0 votes
2 answers
73 views

Experimental errors and significant figures

Textbooks indicate that when reporting experimental results, the number of decimal places in the best estimate of the value (mean) should be the same as that in the standard error, e.g. 9.81 $\pm$ 0....
dgwp's user avatar
  • 429
0 votes
1 answer
72 views

How is it possible to collide particles with specific momentum in microscopic scale?

Quantum theory says particles with almost specific momentum are spatially spreaded. (have relatively large spatial scales). Then how is possible to collide them very effectively in microscopic scale? (...
moshtaba's user avatar
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11 votes
5 answers
4k views

Why has it been so hard to come up with testable predictions for string theory? [closed]

String theory has yet to come up with any easily testable predictions despite decades of work. Why is this? Why is it so difficult to come up with testable predictions for string theory? Why is it ...
blademan9999's user avatar
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0 votes
1 answer
91 views

Particle acceleration - why are colliders seemingly so limited?

I imagine this has been asked before but I am wondering why particle accelerators are so limited. - Why do they have to be big circles? Is there no other technique of accelerating charged particles? ...
Rabbi Kaii's user avatar
3 votes
2 answers
3k views

How can it be "unfortunate" while this is what the experiments want?

In John Gribbin's Ten Tantalizing Truths, the author discusses the cyclotron: for a particular mass as the particles spiral outward, the rotation frequency stays constant, because the particles are ...
Ahmed Samir's user avatar
1 vote
0 answers
69 views

Experimental Demonstration of Entanglement?

In many papers about entangled sources, they use an experimental setup like this one to demonstrate their entanglement: The setup involves measuring coincidences at the detectors at various angles of ...
flevinBombastus's user avatar
0 votes
0 answers
27 views

Numerical outputs of experiments which gives spectrum of blackbody

Many books have spectrum of blackbody radiation in some temperatures before result of Planck and say this is result of experiment. But they don't have any table as result of measurements from them we ...
moshtaba's user avatar
  • 1,409
13 votes
2 answers
183 views

DIY Spectrophotometer doesn't work properly in the IR range

I've built an optical spectrometer by following the instruction given on the Theremino website: Theremino_Spectrometer_Construction.pdf, but I'm having a little issue with it. Everything works ...
Matthew_R's user avatar
  • 321
1 vote
2 answers
217 views

Penrose's explanation of the two-slit experiment

I don't understand what Penrose is talking about in the following paragraph of his book "The Road To Reality". I have read about the two-slit experiment in other texts and I understand it (...
moshtaba's user avatar
  • 1,409
0 votes
1 answer
114 views

Understanding the Uncertainly Principle in Stern–Gerlach experiment

Question is at the bottom, some background info I was watching a lecture where they considered for simplicity sake that the spins were represented as two properties : Hardness (Hard and Soft) and ...
roaibrain's user avatar
  • 101
1 vote
1 answer
96 views

What's an inexpensive way to measure the amount of UV light (or IR light) given off by a light bulb? [closed]

What's an inexpensive way to measure the amount of UV light (or IR light) given off by a light bulb? Specifically, the amount at various wavelengths of UV (and IR)?
user3807846's user avatar
1 vote
0 answers
48 views

Do we experimentally know how a magnet reacts in a curling / non-zero-curl magnetic field?

There are two possible formulas for the magnetic force on a magnetic dipole moment due to the inhomogeneity of the magnetic field: $$ \vec{F}_{A} = \nabla (\vec{m}\cdot\vec{B}) \qquad\text{ and }\...
Maximal Ideal's user avatar
0 votes
1 answer
61 views

What happens when screen is not placed where Image is focused but elsewhere?

When we try to form a real image on a screen by a convex lens, we place the screen at a distance where the image is focused. But if we try to place the screen at a distance less than the distance ...
Garv Chaudha's user avatar
1 vote
1 answer
85 views

Can we design an experiment or an intuitive way to demonstrate tidal locking?

I was explaining the tidal locking phenomenon to a friend. First I started with the formation of solar system and how at the beginning the planets were actually like balls of magma-esque rocks. And ...
polfosol's user avatar
  • 165
1 vote
1 answer
67 views

How do we measure the probability of outcomes in a quantum computer if qubits collapse when measured?

I understand the idea behind Quantum Computing being that we superpose all possible states of a system of qubits and amplify the probabilities of whatever it is that we want depending on the circuit ...
Omeglac's user avatar
  • 109
5 votes
2 answers
1k views

Does the EMF of a battery change with time?

OK, so... I know that batteries provide less and less energy with time. My question is- is that a result of a decrease in the EMF of a cell or an increase in the internal resistance of the cell or ...
Maddy's user avatar
  • 153
4 votes
1 answer
140 views

Are non-virtual particles of QFT real?

Perhaps the question may seem a bit provocative, but it refers to several mathematical and, presently physical facts, pointed out a long time ago: The Unruh effect suggests that an accelerated ...
Davius's user avatar
  • 1,640
2 votes
1 answer
23 views

What are the physical concepts that can be associated with the operation of a hydraulic arm? [closed]

I am developing a project that requires an explanation of the physical concepts behind something applicable, like in the industry. I have chosen to describe the concepts behind the operation of a ...
Gabriel Shiva's user avatar
2 votes
2 answers
66 views

Anisotropic Behavior of Glass in the Faraday Effect Experiment

I'm currently working on an experiment that uses the Faraday effect to determine the Verdet constant of SF-57 glass. Basically, similar to the photo above, I have a LED that generates a 405nm light. ...
Malu's user avatar
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4 votes
0 answers
59 views

How can i find the value of Planck's constant using Black body radiation?

I'm working for a physics project for Highschool, and i'm currently thinking about using black body radiation to measure Planck's constant. I know there is an option using the photoelectric effect but ...
Johnny's user avatar
  • 41
14 votes
2 answers
2k views

What are the experimental difficulties in measuring the Unruh effect?

The Unruh effect was predicted in 1976. As someone with no background in experimental physics I find it surprising this effect hasn't been measured yet. What are the experimental difficulties (and ...
More Anonymous's user avatar
0 votes
1 answer
104 views

Are there enough parameters in standard model to falsify SUSY?

I know that the search for Higgs would be quite pointless if there was no estimation of its mass. Namely the perturbative violation of unitatity, gave us an upper bound on its mass.Unitarity ...
Bastam Tajik's user avatar
  • 1,268
1 vote
1 answer
153 views

Millikan's oil drop experiment [duplicate]

In Millikan's oil drop experiment why oil drop only pick negative charge from gas between both charged plates? Why not oil drop pick positive charge?
Abhishek 's user avatar
1 vote
1 answer
50 views

About the experiment for pressure in solids in thermodynamic

I want to understand something: when someone measure the pressure, temperature and specific volume of a material, I think the pressure is applied in all directions of the material. This can be ...
Julio César's user avatar
1 vote
2 answers
85 views

Had a real experiment ever been done to demonstrate and calculate the magnetic field of a rotating charged disk? Or only thought experiments?

I have been trying to find if a real experiment has ever been done to prove and calculate the magnetic field of a rotating charged disk, whether it's a conducting or a non-conducting charged disk. All ...
MICHAEL DAVE's user avatar
0 votes
0 answers
50 views

How efficient are coincidence counting techniques?

Obviously there is a limitation as to how well experimental configurations that depend on coincidence counting can efficiently remove the noise present at any given experiment. This leads me to ...
OneStrangeQuark's user avatar
4 votes
1 answer
130 views

Why is a large magnetic field problematic (for topological physics)?

In papers studying or searching for topological order (intrinsic or symmetry-protected) in various condensed matter systems (e.g. Field-tuned and zero-field fractional Chern insulators in magic angle ...
mbintz's user avatar
  • 398
0 votes
0 answers
61 views

Twin paradox with communication

Professor Brian Greene covers a unique angle into the twin paradox by having the stationary observer and the rocket release light beams towards each other in fixed intervals according to their proper ...
Alan Whitteaker's user avatar
0 votes
1 answer
28 views

Are there references of influences on physical processes in experiments?

Suppose I have some physical process to use in some experiment. For instance, let's consider just looking at an object to measure its position. The basic modelization for this is to consider geometric ...
Slereah's user avatar
  • 16.5k
0 votes
1 answer
203 views

What is vetoing in the context of experimental particle physics?

I saw in this paper by the CMS Collaboration that two of the selection requirements defining the signal regions are the requirements on $b$ jet veto and $\tau_h$ veto. What is, in this context, a veto ...
jmaguire's user avatar
  • 313
2 votes
1 answer
105 views

Massless electrons pre electroweak symmetry breaking observation

I recently heard that electrons are massless at energies above electroweak symmetry breaking, has this ever been observed experimentally? I looked for it but couldn’t find anything
Simon's user avatar
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