Questions tagged [experimental-physics]

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

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Subtracting background from a radioactive measurement

To measure the activity of a certain sample, we need to also measure and subtract the background. An experiment I attended had explicit instructions that the background should be measured before AND ...
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15 votes
3 answers
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Does gravitation really exist at the particle level?

As I understand, we usually talk about gravity at a macro scale, with "objects" and their "centre(s) of mass". However, since gravity is a property of mass generally (at least ...
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1 vote
1 answer
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How Chadwick concluded that the particles are neutrons but not photons?

James Chadwick conducted an experiment in which he bombarded Beryllium with alpha particles from the natural radioactive decay of Polonium. How he concluded that the radiation was made up of neutrons ...
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1 vote
1 answer
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If I was to take light and loop it between two iron cores, like a transformer with copper; what would happen?

Precursor: I am not a physicist, and don’t claim to be. I’m sorry if the question is easily answered. Question: If I were to take light and loop it between two iron cores, similar to the way copper in ...
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4 votes
1 answer
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Running of the fine structure constant: meaning of $\alpha(Q^2=0)$?

In Measurement of the Running of the Fine-Structure Constant, the L3 collaborations writes At zero momentum transfer, the QED fine structure constant $\alpha(0)$ is very accurately known from the ...
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1 vote
1 answer
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Why lead plate was used in Rutherford's gold foil experiment?

I have read that lead plate is used to concentrate the beam of alpha particles which are being directed towards the gold foil as it is a heavy metal. But there are other heavy metals like manganese, ...
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-8 votes
2 answers
166 views

Can this experiment successfully be used to find out one-way speed of light? [duplicate]

As with almost every question on this topic, this question is also inspired by the Vertiasium video Why No One Has Measured The Speed Of Light. This experiment tries to measure the one way speed of ...
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How was Potassium used to estimate the effect of backgrounds in the Homestake experiment?

I'm trying to understand some of the details of the Homestake experiment, which attempted to measure the rate of neutrino production by the sun. In particular, I'm interested in how Davis et. al. ...
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0 votes
1 answer
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Program to generate graph of spring-mass-damper system

For a school project, I've been researching mass-spring-damper systems. For this I did an experiment in which I basically filmed a spring with a mass attached to it that went up and down and ...
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1 answer
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Has there been any experiment trying to measure the Ricci Curvature of the universe?

One of the major component of the Einstein equation is the Ricci Curvature. As of now, I understand it mathematically as some sort of trace of the Riemann Tensor, and geometrically as the factor by ...
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Experiment of liquid filled rod doing oscillation is called?

I know this is a weird question but I can't find any reference to this experiment, I have Google a lot and now I need the experts help. There is a physics experiment where a liquid filled rod is ...
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-1 votes
3 answers
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Experiments check out theories but who or what checks out the experiments? [closed]

There is a classic saying which goes more or less like this: If your theory is not verified by the experiment then it is wrong! Specifically for the field of particle physics, lately experiments ...
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1 answer
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Pile-up events in collider experiments and the average number of interactions

Is the average number of interactions a measure of the amount of pile-up events (pollution background events to hard-scatter events)? if not, why is always presented as an indication and how accurate ...
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1 answer
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Has the Michelson-Morley experiment been done in space?

Has the Michelson-Morley experiment been done in space? I mean that exact experiment I realize GPS and similar technologies are doing a similar thing. Are any measuring the literal exact same thing.
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1 vote
0 answers
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Calculate the radio of the earth with a stick like Eratosthenes [duplicate]

I read about how to calculate the radius of the earth like Eratosthenes, but they often said that I should measure the shadow of a stick (usually is a stick) at the time when the solar noon occurs in ...
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why do we need lens at fraunhofer diffraction

n Fraunhofer Diffraction, two convex lenses are used. One convex lens renders the incident rays parallel and the other focuses the diffracted ray on the screen.
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2 answers
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Final state radiation and Bremsstrahlung [closed]

Is the final state radiation, whereby a photon is emitted, of a particle caused by Bremsstrahlung, or are the two different effects?
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Magnetic flux from maximum induced emf as a function of angular velocity?

I've done an experiment where I have a small rotating coil in a uniform magnetic field and I've measured the induced emf in the rotating coil as a function of time for several different angular ...
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Where does the error from Origins fitting come from?

Im using Originpro to do some linear fitting of my data points. Origin calculates the gradient and gives an error. Where does this error come from? Ive assumed its how much the data points are ...
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0 votes
2 answers
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Latest experimental evidence for properties of the Higgs boson

I'm trying to find out the most up to date properties for the Higgs boson (like its mass, charge, spin-parity). For now, just focussing on the mass of the Higgs boson, the most up-to-date information ...
1 vote
1 answer
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Using a transparent cup of water as a magnifier

When a transparent glass of water is placed in front of a striped background, it appears to produce this “magnified” view of the background in the center of the cup (i.e., the v shaped blue thing in ...
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1 answer
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How is the Heisenberg Uncertainty calculated value added to a measurement error bar?

It is not clear to me if the calculated HU for a specific experiment is added to the measured value Gaussian curve together with the statistical errors (i.e. added to the total error bar) of this ...
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2 votes
3 answers
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Total standard deviation for a set of measurements

I have a doubt about the calculation of the standard deviation for a set of measurement. To explain better what I mean, I will illustrate what I am doing in my experiment. I am collecting the spectra ...
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How preciece was the CDF II measuremnet?

I encountered an article "High-precision measurement of the W boson mass with the CDF II detector" but I didn't quite understand their result. For example, looking at Fig. 5, there was ...
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0 votes
1 answer
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How long does it take specific types of metal to heat up in the sun?

I'm wondering how long it would take different metals -- for the sake of this question I'll say steel -- to heat up in the sun. Assume it was an 80 degree day and a piece of steel was sitting in a ...
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1 vote
1 answer
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What is the difference of two Chi-square formula, and how can I use them properly?

I found two formula for chi-square: $$\chi^2 = \sum_i ^N \frac{(\text{measured}_i - \text{expected}_i)^2}{\text{variance}}$$ and $$\chi^2 = \sum_i ^N \frac{(\text{measured}_i - \text{expected}_i)^2}{\...
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What recent evidence do we have for higher dimensions? [duplicate]

I realize this question may have been asked some time ago, so do we have any up-to-date data for dimensions other than those of space/time? Also, what do scientists mean by higher dimensions?
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3 answers
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Why does acceleration not depend on mass down an incline?

I understand the net force acting on toy car traveling down an incline is: F = mg sin θ - μ mg cos θ a = F/m Hence mass cancels out leaving: a = g(sin θ - μ cos θ). Intuitively I can't understand why ...
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Test for correlation in photon detection

I have data from an experiment as follows. $x^A_t = [0,0,1,0,2,0,3,...]$ and $x^B_t = [0,1,1,0,2,2,0,...]$. These numbers are photon counts measures in two different photon-counting detectors. I have ...
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1 vote
1 answer
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Mass effects on toy car

In a theoretical experiment with only friction ( With floor and ramp ) and gravity, would the mass of a toy car affect its distance traveled after reaching the bottom of the ramp. My hypothesis is ...
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1 vote
2 answers
46 views

Deducing the velocity field of wind from the motion of plants

I am developing a project for the subject of fluid mechanics and I had a question. The project we want to develop involves using wind and a small hill as a giant wind tunnel. The hill is filled with ...
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Frame of Reference chosen in Hafele-Keating experiment

I do not understand why we chose the frame of reference which is at rest with respect to Earth's center. I get that it does not experience the acceleration due to centripetal force of Earth's rotation ...
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-3 votes
1 answer
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What will be the path of light coming from torch that is lit vertically in a train that is moving at the speed of light compared to the ground?

Assume a train is moving at the speed of light and a person is sitting in the train with a torch. Say the person lit the torch vertically upward comparing to the ground of the train then after the ...
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1 vote
1 answer
47 views

Any details on deep inelastic scattering? [closed]

The article on Wikipedia is rather scanty and I couldn't find more info in previous questions. I hope you will cot consider this as a multiple question since all queries are details of a single issue. ...
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1 vote
2 answers
61 views

What is $M_N$ in the Goldberger-Treiman relation?

$$g_{\pi NN} F_\pi = G_A M_N .$$ Does it stand for the magnetic moment of the neutron? One place I came across it was on Wikipedia, on their QCD Vacuum page, in the section about experimental evidence,...
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2 answers
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Finding the uncertainty in angles that need to be changed to radians, when dealing with trigonometry ratios?

I just wanted to ask about how we are supposed to do uncertainties in our experiment since in they y-axis is acceleration/cosx and on the x axis is tanx. Are we supposed to place error bars on both ...
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2 votes
0 answers
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What would be the impact of slighty higher mass for the $W$ boson? [closed]

With the recent announcement from CDF https://cerncourier.com/a/cdf-sets-w-mass-against-the-standard-model/ placing it at the mass at $$80,433.5 \pm 6.4\; \text{(stat)} \pm 6.9\; \text{(syst) MeV},$$ ...
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2 votes
2 answers
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Does mass affect distance travelled by a toy car?

Say, I conduct an experiment with a toy car and a ramp (Fixed angle). If I were to use the same toy car but place different weights on it (assuming the same size and shape), would the car with more ...
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1 vote
0 answers
50 views

Car with different mass travelling down a ramp

Recently I conducted an experiment at school to see if mass affected the distance travelled by a car after reaching the bottom of the ramp. We used the same toy car and placed different weights on the ...
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0 votes
1 answer
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Measuring radius vs diameter for a circular ring?

Consider an experiment where I have to measure the radius of a circular ring diffraction (or interference) pattern (think Newton's rings). It is advised to measure the diameter and then divide it by ...
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0 votes
0 answers
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Running of the fine structure constant

In Measurement of the Running of the Fine-Structure Constant, the L3 collaboration reports their fine structure constant data for various values of momentum transfer which they call $Q^2$. This is ...
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0 votes
1 answer
32 views

Single slit diffraction with a slit width much larger than the wavelength

It is known that for a diffraction pattern to be strong, the wavelength of incoming laser light should be comparable to the slit size. The reason being if the slit is very narrow it effectly is a ...
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27 votes
3 answers
3k views

What technology is needed for an individual to reproduce the current SI meter and kilogram from scratch?

With the 2019 redefinition of the SI base units, I wonder what kind of technology is needed to reproduce the meter and kilogram in practice from scratch with a tolerance of ±0.1 mm and ±0.1 g? ...
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How does exciting electrons influence permeability?

When Electron Spin Resonance experiments (or Electron Paramagnetic Resonance) are done with DPPH, an applied magnetic field creates Zeeman splittings for free radicals in DPPH. DPPH is surrounded by a ...
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1 vote
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Can I use all 4 sides of a polarizing beamsplitter cube as inputs?

The polarizing beamsplitter cube on the following diagram splits non-polarized light in the input a into 2 orthogonal polarizations: p-polarized light is transmitted into the output c while s-...
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1 answer
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Can an observer visible distinguish between Rayleigh and Mie scattering of monochromatic light by a medium?

Is there a way to visually determine that monochromatic scattered light by a medium is Rayleigh or Mie scattered by this medium? And if there is no way to tell the difference by just looking at it, ...
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2 votes
0 answers
45 views

Recreating the Pound-Rebka (Harvard Tower) Experiment

For my senior lab I am thinking of recreating the Pound-Rebka experiment. Does anyone know if this has been done in a pedagogical setting before and/or knows any resources that would be helpful in ...
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2 votes
1 answer
62 views

How to estimate the experimental acceptance of a particle as a function of its life-time?

My lecturer stated that we can calculate the experimental acceptance of the Higgs boson as a function of the life-time and also as a function of the mass by reading the following article: Davier and ...
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1 vote
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Total brightness from emission spectra?

Some background: I'm looking to analyze stars through a telescope; I'd like get both the visual spectrum and the brightness of each target. I'd also like to have to build/carry as few instruments as I ...
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0 votes
2 answers
86 views

How can we conduct experiments to verify formulas without special equipment? How was it done in the past?

If we wanted to verify experimentally/empirically as laymen without special instruments a formula such as $s=16t^2$ which is used to approximate the distance s, in feet, that an object falls freely ...
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