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Questions tagged [experimental-physics]

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

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1answer
11 views

Experimental preparation of an electron plane wave with given momentum in quantum mechanics

Boiling electrons off a hot filament constitutes a preparation providing a mixed ensemble with nearly Maxwellian distribution of momentum eigenstates. To further purify the ensemble, one can let the ...
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1answer
18 views

How to disturb a particle distribution

I have a set of N macroscopic particles, each representing a group of electrons. Each of these macroscopic particles has a different charge. My system is one-dimensional so all particle´s positions ...
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0answers
21 views

Trouble with Damped Pendulum

For a lab report, I am measuring the impact of initial angular displacement on the stopping time of a pendulum. It is not ideal to swing a pendulum and wait for it stop completely, so I decided to ...
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1answer
49 views

Measuring neutron separation energy

In Introductory Nuclear Physics, Kenneth S. Krane describes neutron separation energy (page 65), and shows a list of measured values (Figure 5.2). What experimental setup is used to measure these on ...
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0answers
37 views

How is a spectrometer is calibrated for intensity?

For the case of spectrophotometers, we can easily calibrate the device(intensity wise) taking the light source inside the device as the reference, without any need of precise knowledge about its ...
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10answers
10k views

Is there any physical evidence for motion?

Let's say that we have 2 tennis balls in space, one being in motion (say, pushed by an astronaut), and the other one still. If we could take a snapshot of both tennis balls, would there be any ...
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1answer
71 views

2019 Higgs Boson Mass?

Wiki, based on the 2018 Particle Data Group, gives the Higgs boson mass as $125.18 \pm 0.16$ GeV$/c^2$. OK. However, 2017 ATLAS gives a combined value of $124.98 \pm 0.28$ GeV$/c^2$. So what is ...
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0answers
27 views

Relation among the dead time, recovery time and resolving time of a GM counter

I have been researching a lot for my assignment about the relation among the dead time, recovery time and resolving time of a GM counter. Most of the articles I came across have varying definitions on ...
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1answer
48 views

Has it ever been possible to measure the fluxes of $\nu_e$, $\nu_\mu$ and $\nu_\tau$ separately?

This is a follow-up of the question asked here. After going through the Wikipedia page on SNO experiment, I need further clarifications about the accepted answer here. First, the SNO experiment ...
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0answers
23 views

How to obtain a relationship between variance and resolution?

In general, resolution can be expressed as a function of the variance of a measured variable. For example the resolution of measuring $x$ can be proportional to $\sigma_{x}$ or $\sigma_{x}/x$ or some ...
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1answer
584 views

Is it possible to actually run Sidney Coleman's “Diehard” experiment?

I just rewatched Sidney Coleman’s famous lecture “Quantum Mechanics, In Your Face”. I say “rewatched” because I had the privilege to attend his repeat of this lecture at UCSD in ’94 or so. But ...
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0answers
10 views

Is there a difference between a electronic force restoration balance and a Kibble balance?

At least from the description of the working principle, the typical analytical balance seems to use the same principle used by Kibble - Watt balance to realize the international standard kilogram from ...
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1answer
86 views

Calculation of final temperature [closed]

what would be the final temperature of any body with the change in the ambient temperature? A Body temperature was recorded at 27.2°C ambient temperature is 60.2°C Final temperature of body is 60....
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0answers
12 views

Advantage of narrow cords in bifilar pendulums

I'm a high school student doing further reading for a project I'm starting and I came across this experiment. On slide eight it mentions that the fibres holding up the pendulum are 0.2 mm in ...
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0answers
19 views

Optimizing flow rate in a pipe

I was recently studying fluid dynamics (volumetric flow rate to be precise), and I was wondering whether there was a method to determine the optimal flow rate of water in a pipe? I was thinking of ...
3
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1answer
84 views

How to know that scientific instruments work?

While reading Zimring's book, What Science Is and How It Really Works, I came across some words on being skeptical about scientific instruments on p.183-184: "The extent to which such instruments ...
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1answer
32 views

Percent difference when both negative

In an experiment, I was asked to find the percent difference between theoretical and experimental $y$-intercept (which I have). It is known that its formula is $$\text{Percent Difference} =\frac{|x_t-...
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0answers
30 views

Question in measurement uncertainty calculation in projectile motion

For a projectile motion, $\displaystyle t=\sqrt{\frac{2y_0}{g}}$. If you look at page 6 of the article(http://www.hep.vanderbilt.edu/~maguirc/Physics231/p231_lect3.pdf), the fractional uncertainty/...
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3answers
79 views

Experimental proof for isospin conservation of strong interaction

I am having a surprisingly hard time to find direct experimental results for the (approx.) conservation of isospin in strong interactions. The canonical examples seem to be $\omega \! \to 3\pi^0$ and $...
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4answers
1k views

How is the speed of nucleons in the nucleus measured?

This article claims that "nucleons in a dense nucleus exceed 25 percent of the speed of light". How do you measure or infer the speed of nucleons in the nucleus? Note added later: I'm looking here ...
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1answer
25 views

Why does a photomultiplier tube (PMT) traditionally present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD)?

Empirically, a photomultiplier tube (PMT) is said to present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD). Some materials say that it is attributed to the higher gain and ...
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2answers
35 views

Linear Regressions vs Algebra & Averaging in Solving for a Constant

I'm current taking AP Physics, and in both of the labs performed so far (Snell's Law/Refraction and Galileo's Inclined Plane), I have been trying to calculate some constant from a linear relationship ...
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0answers
27 views

Jacobian peak in particle physics

The question is related to the derivation of equation (42) in the lecture note of (https://arxiv.org/pdf/1709.04533.pdf). I discussed this with my professor and he seems not interested in such "...
2
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1answer
27 views

How to know what production channel Higgs came from?

There are four main production channels for SM Higgs: ggF, VBF, Higgstrahlung and associated top. In multiple occasion I've seen experimental bounds referring to say $\sigma(gg \to H \to \tau^+\tau^-)...
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1answer
19 views

Would SiPMs respond differently to scintillation light from neutrons vs. gammas?

I have a fast-neutron scintillator which also is sensitive to gammas (much less so, though). When I connect it to a SiPM instead of a PMT, the gamma pulses (obtained from performing pulse shape ...
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0answers
40 views

Design and construction of a system identifying molecular nitrogen and water

I have read papers that use LIDAR-like and LIDAR-Raman systems that detect elements. I want to measure the vapor water ($\rm H_2O$) and $\rm N_2$ of trees/agriculture using Arduino and low cost ...
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0answers
25 views

Step-like contribution to background $\gamma$ ray peaks

I'm reading the paper "Analytical functions for fitting peaks from Ge semiconductor detectors" by R.G. Helmer and M.A. Lee. For $\gamma$ ray peaks the spectral "background" in the region of a peak: ...
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0answers
15 views

How to physically interpret concave multifractal spectrum?

I try to investigate the damage of the metal surface with box-counting method (input data is SEM surface images) - some surfaces give a convex multifractal spectrum [f(α(q))=α(q)*q-τ(q) versus α(q)] ...
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0answers
31 views

Get the number of counts from a Gaussian that fits the logarithm of counts

I have n data to fit: $$x=[\text{channel}_1,\text{channel}_2,\dots,\text{channel}_n]$$ $$y=[\ln(\text{count}_{1}),\ln(\text{count}_{2}), \dots,\ln(\text{count}_{n})]$$ I'm considering a spectral peak ...
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4answers
104 views

How do you do science on Theories of Everything? [closed]

A theory of everything will always have an explanation for why the observed world fits into it's explanation. So cries of "it's not falsifiable!" don't really add anything to the discourse. Of course ...
3
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1answer
105 views

Newtons law of gravity universal?

Im a bit puzzled about the video from “One Minute Physics” claiming that Newtons law of gravity is not universal, but breaks down on very heavy objects and are not really confirmed on very light ones. ...
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1answer
24 views

Is there a wall that can be regarded as an adiabatic wall?

I want to do thermodynamic experiments and need a wall that is approximately adiabatic. Does such a wall exist?
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0answers
18 views

Why *all* the resistances of the bridge need to be of the same order for maximum sensitivity?

Consider the following Wheatstone bridge. I understand that for maximum sensitivity of the bridge (at the balance point), the ratio of $P$ to $Q$ must be $1$. A derivation of this can be found here. ...
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1answer
29 views

Why photodiode measures random phase superpositions on continuous-wave (10kHz) white light?

I measured a 10 kHz modulated white light using a photodiode (Thorlabs PDA10A): Unexpectedly, the photodiode output sensitively depends on the orientation and position of the photodiode. For two ...
2
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1answer
63 views

Theoretical justification for the range of validity of the approximation $R(T)\approx R(T_0)[1+\alpha (T-T_0)]$

In the experiment for calibrating a platinum resistance thermometer, we are always approximating the resistance of the platinum thermometer by $$R(T) \approx R_0 (1+\alpha T),$$ taking the reference ...
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0answers
25 views

What physical interpretation can we derive from this experimental step up?

(This is not a homework question!) An experimental set up shows 2 rigidly placed stands, with pieces of metal links joining with each other forming a chain. The chain is hung from the top point to ...
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0answers
18 views

Electric Field within and outside a plasma ball

According to the electric field strength's equation, electric field strength is inversely proportional to square of distance. Thus, electric field strength gets weaker as it is further away from the ...
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1answer
38 views

Spinthariscope with Uranium pottery / marbles instead of Americium

Usually home made zync sulfide spinthariscopes employ Americium 241 from smoke detectors as an alpha radiation source. Uranium glazed pottery (e g. fiestaware) and uranium 'glow in the dark' marbles ...
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1answer
30 views

Using height to calculate Pressure (independent variable) and Flow rate (dependent variable)?

The investigation is experimentally verifying Poiseuille's equation. The independent variable is the changing pressure and the dependent variable is flow rate. My experiment plan is having a simple ...
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2answers
28 views

Johnson Noise experimental measurement

How can we experimentally find out value (extent) of Johnson Noise of any resistor with certain bandwidth and teperature?
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1answer
18 views

Experiment for measuring flow rate vs diameter

I am trying to establish the relationship between the diameter size of a pipe and the flow rate water. The main idea for my experiment would be to run water through pipes of varying diameter and ...
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4answers
131 views

Philosophy of Science: Do electrons exist, or are they just models to explain physical phenomena? [closed]

I didn't find any SE site for "Philosophy of Science" hence I am asking it on Physics SE because it is related to Physics more than to Philosophy. As law of gravitation is a model which was proposed ...
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1answer
29 views

How to explain the difference of attenuation of different pitch of sound by kinetic molecular energy?

How to explain the difference of attenuation of different pitch of sound by kinetic molecular energy ? I know that «sound of low frequencies travel farther in air than sound of high frequencies». ...
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0answers
49 views

How come that the magnetic field is not uniform around a trace over a ground plane

I have conducted an experiment, which for me gave some quite unexpected results. I measured the amplitude of a magnetic field around a conductor and expected to see an amplitude that decreases with ...
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0answers
90 views

Effect of metal disks on diffraction of light [closed]

Recently, I started to go deeper into physics. I don't speak English well, so I'm sorry. This experiment was carried out in Hungary 25 years ago. The measurement results were not accepted by the ...
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1answer
33 views

Magnet cores with high permeability but no ferromagnetism?

I have a lab exercise I've been doing with my students for years, in which they suspend two steel balls at unequal heights from steel-core electromagnets, then break the circuit and drop the balls. By ...
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1answer
15 views

Hydraulic analogy for electrical compounds

I want a source (website or a book) where there are hydraulic simulation (or analogy) for all (or at least the most useful) electronic compounds?
1
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1answer
32 views

Error on the mean of several measurements with error

I have some measurements of the same quantity, using instruments of different resolutions. So I have some data of the form $x_i \pm \delta x_i$. I want to report the value obtained from these ...
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2answers
98 views

What is the experimental evidence for gravitational time dilation?

There are many experiments done to prove time can be changed. I don't know lots of them, but I think the most popular (most cited) is to put a clock on a fast moving object (airplane), fly around and ...
4
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3answers
159 views

Is gravity a factor for sustaining fusion?

Does gravity affect a Fusion reactors ability to sustain a reaction? If so has there been any experiments done or planed for in space? Holding / maintaining shape might be a lot easier with less ...