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

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1answer
39 views

Could satellites achieve orbit using current laser technology

My question is, could we, using current laser technology sufficiently scaled up, launch a lightweight, say a GPS navigation satellite, into earth orbit? The main objection to me is maintaining the ...
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2answers
878 views

Show that a photon cannot transmit its total energy to a free electron. Contradiction with Photoelectric effect?

This is a problem in my textbook and I've shown it this way: $E_{initial}=\frac{hc}{\lambda} + mc^2$ $p_{initial}=h/\lambda$ After collision with photon having zero energy we get ...
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1answer
26 views

Explain an experiment: airstream between two hinged curved surfaces

Please, see the following video (the experiment starts at 3:40 and ends at 3:55): https://www.youtube.com/watch?v=7pB6q_bH35s&feature=youtu.be&t=216 The basic idea: given 2 curved surfaces ...
13
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1answer
359 views

Does my green laser pointer emit three distinct frequencies, or is my measurement flawed?

I was playing around with a cheap diffraction grating and my set of laser pointers, and I noticed that while the red and the blue pointers produce a single point in the spectrum, my green laser ...
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0answers
42 views

How much does barometric pressure change over minutes?

I have to correct an ongoing experiment for atmospheric pressure. This means that during the experiment I must read a chip that measures barometric pressure. The question becomes one of how rapidly I ...
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1answer
85 views

About recent experimental evidence of Majorana edge states in topological superconductors

I have a couple of question about the recent experimental evidence of Majorana edge states in topological superconductors. Which are the main differences between the experimental signatures of ...
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1answer
112 views

Physics involved in the DNA-structure discovery

In 1962 Francis Crick, James Dewey Watson and Maurice Hugh Frederick Wilkins won the Nobel Prize: For their discoveries concerning the molecular structure of nucleic acids and its significance for ...
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1answer
57 views

Why is a substrate needed in growing GaN?

Is the substrate a layer on which GaN crystal grows on? Is there a way to grow free-standing GaN? Would the resultant crystal be full of defects?
2
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2answers
452 views

Free parameters in the Standard Model

From my understanding of the standard model, I understand that there are 19 or 20 free parameters that we need to put in by hand as, and I'm guessing here, there is as yet no theoretical basis for ...
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0answers
110 views

Measuring electrical conductance (resistance) of ice and water

What is the standard method of measuring conductance of ice and water? The reason I ask is that apparently one has to take account of the fact that both of them conduct electricity protonically ...
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0answers
44 views

Trying to understand electron diffraction

I'm trying to understand how electron diffraction works, but I'm not really getting it. Here's an image Here are a couple of questions about it that I can't figure out. Why is the angle of the ...
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1answer
63 views

Propagation of uncertainty - which formula? [duplicate]

Can someone explain to me when do I use this formula ...and when do I use this one?
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2answers
59 views

Energy for burning things!

I have a cylindrical lens & a surface that can be burned.( for example wood , sheet ,...) In a sunny day , I wanna burn the surface but I don't know the "Energy for burning surfaces" If the ...
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1answer
123 views

Amplitude-Frequency curve

Given a resonance curve just like this: Could someone explain to me what the physical meaning of the intersection with the ordinate is? At first glance I would say it has to be $(0 | 0) $ since ...
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0answers
77 views

Directions in the Elastic/Stiffness Constant Tensor

I am working on a report for an experiment I did concerning the Elastic constant tensor. This has 36 terms for tensile and shear stresses. I don't understand what the off diagonal elements are! C11 is ...
2
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0answers
24 views

How do I calculate temperature diffusion in a gas contained in a heatsink?

To simplify the problem, consider a sphere with a diameter of $25\mathrm{mm}$ inside an infinite heatsink at $300\mathrm{K}$. At $t=0$ I instantaneously raise the temperature of the gas in the ...
1
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1answer
199 views

Torsion pendulum and determining the moment of inertia

(58. Polish Olympiad in Physics, final stage, 2009) We have a given element . We have to determine its moment of inertia. The idea is using a torsion pendulum. Some considerations lead us to a ...
2
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1answer
54 views

Experiment irreproducible because laws of physics change

In a comment to a recent question, "LHC: Irreproducible results: when/where else have we put so much trust in one test facility?", aandreev said "formally speaking, every experiment is irreproducible ...
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0answers
26 views

Losses in a laser diode

How do I convert loss/gain from units of /cm to /s? Intuitively, I would say multiply loss in /cm with the group velocity c/n, where n is the refractive index. Am I missing anything?
2
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1answer
83 views

Can a nuclear bomb be used as the power source for a laser beam

My previous post "Using nuclear bombs to detect near earth orbit objects" asked about using nuclear devices to detect Earth directed asteroids and low albedo comets. Now I want to explore a method of ...
2
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1answer
104 views

Using nuclear bombs to detect near earth orbit objects

This question is based on an article written some years ago by A. C. Clarke, in which he attempted to solve two problems with one solution. His idea was to remove the Earth's stockpile of nuclear ...
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3answers
371 views

Can the Unruh effect be confirmed by the LHC?

Two short questions regarding the Unruh effect. There are related answers on this forum and on wikipedia, but I am looking for confirmation of my own intuitive assumptions, so a straightfoward yes or ...
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0answers
59 views

Spectral Response of a photo-resistor (CdS) and phototransistor (Si)!

I am doing a report on an experiment I took and I have completed every section apart from this last bit. I am told to compare the spectral response of a CdS and Si. I am unable to construct a graph ...
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2answers
430 views

Evidence that nuclei contain neutrons and protons (other than nucleons appearing if a nucleus is smashed)?

This may seem like a silly question, but I believe this to be very fundamental because the Standard Model of particle physics seems based on the axiom or assumption that neutrons and protons exist ...
3
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2answers
524 views

Water Waves in the Wake of a Boat

As a boy I noticed that the waves from the wake of my model boat would fan out. If I looked at the end furthest from the boat the front had turned so that it was almost running in the same direction ...
2
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1answer
57 views

How is the the lower-limit of the proton lifetime measured experimentally?

Wikipedia says : Recent experiments at the Super-Kamiokande water Cherenkov radiation detector in Japan gave lower limits for proton half-life, at 90% confidence level, of 6.6×10^33 years via ...
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3answers
266 views

Has anyone tried Michelson-Morley in an accelerated frame?

After doing much more digging than I thought I had to do, I found out that the speed of light is NOT invariant in an accelerated reference frame. Has anyone done any experiments to confirm this? In ...
3
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3answers
406 views

What would happen to me if I was in the LHC while it was running? [duplicate]

This is possibly a stupid question, but one I have been always wondering. What would happen to me if I was in the center of the Large hadron Collider while it was running? Would the energy of the beam ...
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0answers
24 views

What is the spin of a magnetic impurity?

I am reading this seemingly important paper Local Magnetic Moment Associated with an Iron Atom Dissolved in Various Transition Metal Alloys. It is strange to me that the magnetic impurity has ...
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3answers
103 views

Double slit experiment

What's the simplest way to describe and show the double slit experiment? I have to perform an experiment proving how it all works in my physics class.
3
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2answers
63 views

Optimizing surface geometry for thermal radiation

I'm working on vacuum technology for a scientific project and one of the challenges is to optimize the cooling of 2500°C metals in vacuum. I'm wondering if it would be useful to design a grating on ...
0
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2answers
54 views

wormhole time machine and violation of uncertainty? [duplicate]

Let's asssume we have a wormhole that allows sending info to the past and receiving information from the future. Next, we have a particle moving in two dimensions, for which we can evaluate $ p_{y} $ ...
2
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1answer
43 views

What is the difference between a measurement and an experiment?

For example, say I want to determine the atomic structure of a bio molecule. I purify the molecule, get it to crystallize (probably though trial and error), shoot it with X-rays, observe the scatter ...
38
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4answers
5k views

Can water falling from a tap follow a spiral path?

The faucet design depicted below is driving me crazy. The water falling from the tap appears to follow a spiral path. No one seems to agree whether it is physically possible for the water to spin in ...
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3answers
102 views

Mathematical formula for hysteresis [closed]

For my final year project, I need to design a lab to generate a hysteresis loop. But I have no idea how to do it. Is there any mathematical function or any code or any article which would help me to ...
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0answers
25 views

ZnO nanorods synthesis

Could someone please let me know the steps to be used for sol-gel method synthesis of ZnO nanorod arrays using PVA as solvent and Zn acetate as precursor? I need vertical and uniformly aligned NR ...
2
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0answers
80 views

How do we get the power spectrum through the CMB?

How do we get the power spectrum through observing the CMB?
2
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5answers
527 views

Where does General Relativity (GR) fail experimentally? Experimental shortcomings of GR?

When speaking with researchers and professors at my physics department, I sometime catch this undertone in the conversation when speaking about GR: almost as if some are not entirely convinced about ...
0
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2answers
178 views

Is the intuition of “absolute simultaneity” necessarily wrong?

I read about Einstein’s theories of relativity with all the interesting stuff like time dilation, mass increase and whatnot. And also about the relativity or conventionality of simultaneity. The ...
11
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2answers
658 views

Sun spectroscopy - Home experiment

We let the sun light run through a 5x3x3cm triangular glass prism and we examined the formed 'rainbow' in search of Fraunhofer lines. However, even though we looked close enough (even with a ...
0
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1answer
61 views

Light speed measured by observing Jupiter moons [duplicate]

The famous discovery that the light has speed measures the times of the immersion and emergence of Io, one of Jupiter's moons. However, I still can't comprehend this. Even when the Earth is further ...
1
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1answer
78 views

How are energy states of photons reason for frequency independence in Compton scattering

I am reading on Compton scattering, more specifically on how Compton interpreted his results. He observed that the frequency of the scattered radiation was independent of the material used, so he ...
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2answers
222 views

What kinds of behavioural anomalies can a zero-field-cooled (ZFC) / field-cooled (FC) split indicate?

If a material shows a spiltting in the ZFC and FC curves, is it necessarily superparamagnetic, or could there be any other reason for the irreversibility? I have heard spin glasses also show ZFC-FC ...
0
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1answer
35 views

Why friction is not taken to be varying jointly as roughness of the object along with normal force?

Frictional resistance to the relative motion of two solid objects is usually proportional to the force which presses the surfaces together as well as the roughness of the surfaces. But when we talk ...
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2answers
70 views

If two bodies move opposite to each other when brought in contact, what is the direction of force of friction?

We know that when a body is at rest and other is dragged over it then a force is produced which opposes the motion and consequently its direction is negative to the force applied on body to produce ...
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0answers
25 views

Such high mobility value for degrading structural properties

I have prepared Cu enriched ZnSe thin films with different concentrations of copper. The XRD and RAMAN results showed improvement in structural properties as the Cu content is increased up to 10%. ...
0
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1answer
107 views

Did Don Borghi's experiment show that neutrons can be synthesized purely from protons and electrons?

C. Borghi, C. Giori, and A. Dall'Olio published an article entitled "Experimental evidence of emission of neutrons from cold hydrogen plasma" appearing in Yad. Fiz. 56, 147-156 (July 1993) and Phys. ...
2
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1answer
173 views

Which g factor in an EPR spectra is the right one?

I was reading this introduction to EPR and it seems to imply both that there is a unique g-factor of a given compound, but also that we can calculate multiple g-factors for a compound. For example, ...
0
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1answer
59 views

How to derive time derivate of strain?

Data Time(s) Strain ----------------- 100 0.31 200 0.52 300 0.74 400 0.92 500 1.10 600 1.28 700 1.46 800 1.64 900 1.82 1000 2.00 I want to deduce ...
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3answers
203 views

How to find dielectric constants of ferroelectric materials experimentally?

What is the procedure to find out dielectric constant of barium titanate at different temperatures ?