Questions tagged [experimental-technique]

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

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1answer
668 views

Calculate the diameter of of Gaussian beam at FWHM (or at 1/e2)

I need to collimate a gaussian laser beam out of a single mode fiber (NA0.15) with a single lens so that the full-width half maximum (FWHM) of collimated beam is 10mm. This question may sound naive, ...
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443 views

FTIR powder sample without KBr - is it allowed?

My team measures some nanoparticle powder in reflectance mode. In all the sources [1][2][3] I found that for powder measurement you need to mix it with KBr. However my team just put manually ...
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125 views

Nonlinear Response of CCD camera

What is meant when it is said a CCD's response is nonlinear? Does it mean the value of a pixel of the camera is not proportional to the number of received photons? Does it involve saturation? What ...
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1answer
3k views

What is the principle behind schuster focussing?

Schuster Focussing is often used to focus the collimator and the telescope for a parallel beam of light. What is the underlying principle behind the procedure? How is it related to the fact that 2 ...
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1answer
65 views

'Error on the order of 0.5cm'?

This is a quick question about reporting approximate errors in a physics lab report. There was an error which I did not account for exactly in my experiment, but I want to acknowledge it as a source ...
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1answer
437 views

How is spectral energy density measured?

It has been my misconception that Plank's law for black body radiation is a function that relates intensity of cavity radiation to energy of radiation & temperature of the walls of the cavity. ...
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2answers
508 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?
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88 views

The radiation pattern of six dipoles in phase and in series

I am reading Feynman Lecture, Volume I, and I have a question on the linked chapter about interference. In 28-4 he discusses the radiation pattern of two dipole radiators, and discusses how we can ...
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2answers
67 views

An experimental setting from Feynman to measure radiation

I am reading the famous Feynman Lectures, Volume I, the section about electromagnetic radiation. After defining what radiation is (the part of the electric field induced by the acceleration of a ...
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1answer
162 views

In the Pound Rebka Experiment, how were the gamma rays generated?

Lest my question be dismissed as poorly-worded, let me first say that I do understand the concept of how a gamma ray is emitted when an electron in an excited (higher energy) state transitions to a ...
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2answers
99 views

How does the divergence of the B field is zero imply that neutrons only “see” spin components perpendicular to the scattering vector?

The following statement is made in a text with no further explanation: "...a direct consequence of Maxwell's Law $\nabla \cdot B = 0$ that implies $B(q)$ has no component parallel to $q.$ This means ...
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1answer
469 views

Why does radiometric dating tell us the ages of rocks?

I understand well how radiometric dating works in theory. In practice, I'm not sure how one would calibrate this for rocks. I've always been told that we can determine rocks' formation time via ...
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1answer
619 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 ...
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3answers
195 views

How are photons told apart by a PET scanner?

From what I've read, a radiopharmaceutical, such as FDG, enters a body and emits positrons that annihilate with electrons, emitting two equal gamma rays in opposite directions. Diametrically opposite ...
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160 views

Doppler Shift of a source that oscillates in Simple Harmonic Motion

I am doing an experiment where I am measuring the Doppler Shift of an object that is oscillating in Simple Harmonic Motion. Experimental Setup Take a spring and attach it to the ceiling Attach a ...
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0answers
25 views

Experimental question regarding uncertainties

I am not sure exactly how to deal with my uncertainties from an experiment I recently did. While taking measurements, I estimated an uncertainty in each result based on my ability to accurately read ...
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1answer
91 views

How to take measurements for wavelength in an experimental wave tank?

To anyone familiar to the experimental hydrodynamics field, how does one experimentally measure the wavelength of the waves generated in a plunger type wave tank or any wavetank for that matter. From ...
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1answer
115 views

Can two electromagnetic fields from different types of sources exist in the same space?

Can a high intensity EM field from an electromagnet and an EM field from a high voltage power line occupy the same space? What effects would one have on the other? Would a magnetic field from a solid ...
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3k views

Is there any advantage in stacking multiple images vs a single long exposure?

Suppose I have a source object that is not time varying, to be concrete let's say it's a galaxy. Is there anything additional that can be learned or done with multiple short exposure images of exactly ...
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1answer
50 views

What special feature does this kind of coupling have?

This diagram was in the 4th chapter of the book Heat and Thermodynamics, Zemansky and Dittman. An amount of gas confined to a cylinder of thermally insulator material, here, is undergoing an ...
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2answers
472 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 ...
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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 ...
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2answers
87 views

Demonstrating that water density is at its maximum at 4 degree

I want to demonstrate to the students this fact in class. I checked the density of water as a function of temperature. The variation is minute, on the scale of one in ten thousand, from 0 degree to 4 ...
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1answer
74 views

Does a mirrored optical chopper wheel exist?

I have a pulsed 30Hz 532nm laser for which I would like 29 pulses to follow one optical path but for 1 pulse per second to be diverted onto a different path. I thought I could simply google for a ...
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1answer
45 views

Using a Ring Imaging Cherenkov (RICH) detector

I'm not clear on how RICH (Ring Imaging Cherenkov) detectors identify particles, as much as I've tried to read up on it. So they measure the angle Cherenkov light is emitted at, which is related to ...
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1answer
94 views

Direct measurement of the mass, charge and spin etc of the particles produced in colliders

My impression is that particle colliders produce particles. Then the detectors measure the amount of the scattered flux of particles in a given direction and compare that with theoretical scattering ...
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1answer
67 views

How do experimentalists find their nanoscale creations?

I am reading up on hyperbolic metamaterials and investigating processes like sputtering and electron deposition to create substrates only nanometers thick. For reference, see this paper by Lu et al ...
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6answers
1k views

Measuring air density - where is my huge error coming from?

I'm teaching a home-schooled 13 year old some physics and chemistry, and last night's experiment was an attempt to measure the density of air. Using an electronic balance that has proved pretty ...
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1answer
85 views

Assistance in Francis Turbine Lab Experiment

Lately I did Francis Turbine Experiment at my institute. The objective was to find the efficiency of the turbine. Power input was found using flow rate and pressure gauge. Power output was found by ...
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2answers
241 views

How do I assess the linearity of a photomultiplier tube?

I have used a scintillation counter coupled with a photo-multiplier tube to record the gamma spectra for sodium-22, cobalt-60, and Cesium-137. I need to know how to assess the linearity of the photo-...
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1answer
72 views

How to detect femtosecond pulses with slow PMT's?

In pump-probe measurements, we can use femtosecond lasers to study ultrafast processes, such as molecular vibrations. PMT's are very slow compared to the pulses, so how can we use them to detect such ...
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37 views

How do I model this experiment for a real world analysis?

I did an experiment of finding the band gap of semiconductors. In this I determined the energy gap of the material of the given thermistor. I was wondering how many parameters must be considered that ...
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1answer
47 views

Currently achievable spatial resolution in photon detectors?

Suppose one wants some 2D detector that measures the positions of photons incoming transverse to the detector; something like an array of photomultipliers. What kind of spatial resolutions are ...
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1answer
78 views

Energy of Big Bird neutrino from IceCube

Big Bird neutrino event has announced two different energies: 2.004 PeV, 2.2 PeV. Both values are scattered over web. It may be that the lesser value is for detected "deposited" energy, while the ...
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3answers
981 views

High School Experiment : Effect of Temperature on Strength of Magnet

I am running an experiment for my school which investigates the effect of temperature on the magnetic field of a magnet, and I encountered a little problem. For the measurement of data, I have gotten ...
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1answer
598 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?
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155 views

Why isn't cosmic microwave background radiation on Earth drowned out by thermal noise

The Penzias/Wilson experiment, which detected the CMB, doesn't sound feasible given thermal noise. When Penzias and Wilson reduced their data they found a low, steady, mysterious noise that ...
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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. ...
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68 views

What difference does it make if the turns in a tesla coil overlap?

Would a tesla coil in which the primary coil is made by overlapping the turns of the wire work?
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2answers
547 views

Pound-Drever-Hall frequency stabilisation technique

I am having some difficulty understanding the Pound-Drever-Hall frequency stabilisation technique, when locking a laser to a stable cavity. As far as I understand: We emit the laser frequency, f0. ...
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48 views

Galileo's pendulum and any references

In some texts about the simple pendulum we use to see references about some "experiments" Galileo Galilei did realize and whereby he found some important results, including that the period of the ...
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1answer
62 views

High $p_T$ and high $Q^2$ in deep inelastic hadronic collisions

When reading about high energy collisions (for example proton-proton collisions at LHC), I always find the relation $Q\sim p_T$, which, for me, is hard to demonstrate. Moreover, I found statements ...
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1answer
70 views

Is it possible to measure the resistivity of something using A.C. Current and a capacitor?

I've read that A.C. current "passes" through a capacitor. Is it possible to use this and measure the resistivity of the medium between the plates? Any sources or links would be appreciated.
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1answer
95 views

Why does a CfBe neutron source not exist?

Sources such as AmBe take advantage of Beryllium's $(\alpha,n)$ process to produce high energy neutrons. Sources such as Cf utilize spontaneous fission. Why not combine the two? Such a source would ...
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2answers
180 views

Muon lifetime determination

My colleagues and I performed several experiments to determine the lifetime of the muon (from secondary cosmic rays) using scintillator detectors coupled to multi-channel analysers. The results ...
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216 views

Why do we learn only two computations, cross sections and decay rates, in such a fundamental theory as QFT?

When I learned Newtonian mechanics I found a vast variety of computations that I could do and that was so interesting. And it was so when I learned Maxwell theory. When I started learning QFT I hoped ...
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1answer
371 views

Can vernier scale ratio be less than 1?

I came across a question (See Image) that states about two vernier scales The first vernier scale is the top-most figure in the image: It has 10 vernier scale division equal to 9 main scale division (...
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1answer
56 views

why am i getting lower mass after melting iron dust?

I've been trying to melt iron dust for a long time but after melting I lose a lot of mass. Any idea what is causing this? I've used gas and electrical arc to melt the dust.
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1answer
187 views

Optical Retroreflectors: How Are the Faces So Accurately Righted?

This question is about Optical Retroreflectors (corner cubes) and how the extreme precision in their manufacturing is achieved. I suspect there is interesting basic physics involved, which is why the ...
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1answer
108 views

How to make a monocrystalline silicon seed

I do understand that you can grow monocrystalline silicon from an initial seed but I'm lost in a chicken versus egg situation where I don't understand how you can get the seed if the only way to make ...