Questions tagged [experimental-technique]

filling in the unspecified details of elegant-sounding descriptions of experimental methods.

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35
votes
4answers
5k views

Double Slit Experiment: How do scientists ensure that there's only one photon?

Many documentaries regarding the double slit experiment state that they only send a single photon through the slit. How is that achieved and can it really be ensured that it is a single photon?
23
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4answers
20k views

How do astronomers measure the distance to a star or other celestial object?

How do scientists measure the distance between objects in space? For example, Alpha Centauri is 4.3 light years away.
6
votes
1answer
567 views

How do we perform transverse measurements in a two level system?

In quantum mechanics any two level system can be mapped onto effective spin variables. If the system is defined by two energy levels, $|E_1\rangle$ and $|E_2\rangle$, the Hamiltonian is $$ H = \left(\...
11
votes
2answers
13k views

Multiple measurements of the same quantity - combining uncertainties

I have a number of measurements of the same quantity (in this case, the speed of sound in a material). Each of these measurements has their own uncertainty. $$ v_{1} \pm \Delta v_{1} $$ $$ v_{2} \pm \...
13
votes
2answers
2k views

What's the problem with my Young slits experiment?

My Young's slits experiment doesn’t work. I mean I tried to see wave effect of light but I didn’t see any thing expect particles! I’ve sent you a pic of my laser and a short video of the experiment. ...
3
votes
2answers
378 views

What is the highest accuracy of measuring time differences achievable today?

I was wondering if it would be possible to shorten the distance between detectors when measuring the speed of neutrinos to, say, 7m rather than the current ~700km? In this way the distance traveled ...
9
votes
1answer
613 views

Why squared mass difference between neutrino 3 and 2 is a absolute value?

why in the case of MINOS experiment (for neutrino mass detection) the squared mass difference of neutrino 3 and 2 is a absolute value(mod) compared with KamLand experiment?
4
votes
3answers
3k views

How to determine whether a large container is air-tight?

In constructing a kitchen-waste digester at home, I use a 50 Litre HDPE drum. The base of the drum is holed with a plug fitted to allow drainage when necessary. The top has two openings - one for ...
3
votes
1answer
1k views

Why is 2-terminal sensing less accurate than 4-terminal sensing if the internal resistance of leads is known?

I have a pretty good understanding of 2-terminal vs. 4-terminal (kelvin) sensing measurements. I understand that in the 4-terminal measurement, current is supplied by 2 terminals that are separate ...
2
votes
1answer
168 views

random triggers

I understand that a small proportion of events at the LHC that would not trigger on any deterministic trigger are saved on what might be called a random trigger, so that, amongst other uses, proposed ...
25
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8answers
6k views

Given fluids expand non-linearly, how were physicists able to make a linear temperature scale?

Materials expand with increase in temperature. As far as I know this property for fluids was put in use to make initial thermometers. We know that expansion of fluid is given by the following formula (...
13
votes
3answers
3k views

Measuring the effective mass

Intro: To avoid any terminology confusion, this is asked in the context of Solid State Physics and semiconductors. The canonical definition given for the effective mass is that it is related to the ...
16
votes
3answers
1k views

How can we 'see'/measure/detect particles during experiments?

I often read (high-level, conceptual) articles and news on the advances of particle physics. In these, statements are made along the lines of 'particle X splits into particles Y and Z which exist for ...
4
votes
1answer
892 views

How do you measure a particle's postion or momentum?

This question is about the Uncertainty Principle $$\sigma_x \sigma_p ~\ge ~\frac{\hbar}{2}.$$ Looking at the maths, I understant why the uncertainty in the poistion increases as the uncertainty in ...
9
votes
2answers
2k views

Mechanical Equivalent of Heat

Recently I have been looking up James Joule's experiment regarding the mechanical equivalent of heat. After viewing some drawings of the apparatus, I assumed that the lines holding the weights would ...
4
votes
2answers
4k views

Strategies against 50 Hz mains hum on detector signals?

I'm having problems with a strong 50 Hz mains hum on signals created by photodetectors. I assume that they are due to ground loops and I realize that the best option would be to remove those. What are ...
3
votes
1answer
218 views

Lectures on experimental optics

I am a graduate student supervised by a computer scientist. We work on projects that require heavy experimental works on optics, for example a complicated self-built telescope, where many lenses, ...
3
votes
2answers
486 views

Identifying the Higgs boson at LHC

In quest of confirming Higgs boson's existence, particle collisions were observed at the Large Hadron Collider. Scientists had to distinguish the observation of the background noise/fluctuation and ...
3
votes
1answer
132 views

How to make sure that two electrons collide head to head?

In high energy experiments, people smash particles into particles. But how to make sure that they really run into each other, instead of just passing by?
6
votes
1answer
733 views

What are the “x” marks in a bubble chamber image?

Upon looking at a decent number of bubble chamber images I noticed an x shape . What particles are producing these trails?
3
votes
1answer
84 views

Machine readable database of gamma lines

Friends of mine did a lab experiment where they recorded $\gamma$-spectra in the range from 0 to 1500 keV with a soil sample. The data contains some background and a couple sharp peaks at different ...
3
votes
1answer
449 views

What algorithms are used for track reconstruction in cloud chambers?

In particular I'm interested in any algorithms that can separate multiple tracks from one another reliably.
2
votes
1answer
80 views

Experimental considerations for measuring the gravitational constant/effects, with two large (1000kg) masses orbiting each other? [closed]

So @uhoh, wanting to get some experimental data to verify Limits on non-Newtonian gravity at length scales larger than 1 meter?, proposed an experiment: Place two large (1000kg) spherical masses in ...
1
vote
2answers
516 views

How to deduce the charge of an electron from the charge of an oil drop in the Millikan experiment?

In the Millikan experiment we measure the charge of one oil drop. But how can I measure charge of one electron when I’m not sure how many electrons are contained within one oil drop?
1
vote
1answer
689 views

Are there any other notable assumptions I've missed in my lab write-up? [closed]

Let's say I have to write a lab report that includes notable assumptions made that are pertinent, significant and relevant to my experiment. The purpose of my experiment is to determine the ...
0
votes
1answer
943 views

Calculational method for determining surface tensions from photograph of menisci?

How can I get from a photograph of a liquid surface to a value for the surface tension.
-2
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1answer
101 views

X-ray: Observation of absorption edge [closed]

So I am working on this experiment on X-ray and kinda stuck on this last and following section. I have done the measurements and plotted the graph as required in 1. and 2. See below, However, I ...