0
votes
1answer
46 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.
0
votes
0answers
28 views

Gaining some intuition: Photon bunching

This is a very easy question: I'm in need of some intuition on the fact that, e.g. thermal sources, produce bunched photons. It is very easy to "undertand", without any quantum mechanics, why single ...
0
votes
1answer
12 views

If cathode rays travel from the cathode to the anode how do they make zinc sulphide glow?

So I basically learned about cathode rays today, and I had a lot of questions in mind. So my textbook says cathode rays travel from the cathode to the anode. So it further says that to observe ...
4
votes
2answers
52 views

Analysis of a system consisting of a leaking tank of water

The departure point is this problem: A water tank on wheels is moving over an horizontal trail with negligible friction. There is a small opening in one of the walls, at a depth of $h$ below the ...
22
votes
4answers
3k views

How do those T-shirts that change color in the sun work?

When I was a kid, I asked my dad about them and he said (not in so many words) that it was because sunlight and artificial light have different spectrums and they picked colors that reflect only the ...
0
votes
1answer
40 views

Why does a bungee jumper continue to move downwards beyond the equilibrium position of the jumper and cord?

When a bungee jumper jumps, ignoring the mass of the bungee cord, the jumper initially falls in freefall before an inelastic collision occurs between the jumper and cord, and the cord extends as the ...
0
votes
0answers
11 views

Diffractive peak for high-frequency scattering from a sphere with small index of refraction?

How does a transparent sphere's shadow fade as $n\to 1$? Consider radiation of wavenumber $k$ incident on a transparent sphere of radius $a$ and index of refraction $n$ in the limit $ka \gg 1$. ...
-1
votes
0answers
52 views

How to find the correlation function? [on hold]

I have an operator $\hat{a}(t)$, and the its correlation is given as: $$\langle\hat{a}(t)\hat{a}^{\dagger}(t^{\prime })\rangle=\delta(t-t^{\prime})$$ Then how can I find the correlation function in ...
0
votes
0answers
21 views

Does photon experience time? [duplicate]

According to the special theory of relativity, for all observers the speed of light is c. Any observer travelling at the speed of light c does not experience time. Hence even protons shouldn't ...
0
votes
2answers
33 views

How do you calculate the intensity of the $m$'th fringe in a Young's slits diffraction pattern? [on hold]

I'm preparing for an exam on wave optics and am struggling with part d) of this question: c) A beam of coherent monochromatic light (wavelength=500nm) is incident normally of a plane of two slits ...
3
votes
1answer
55 views

Vacuum expectation value in presence of a source

If a vacuum is translationally invariant i.e., $P^\mu|0\rangle=0$ or $e^{(\pm ip\cdot x)}|0\rangle=0$, we can express the the vacuum expectation value of a field as $\langle 0|\phi(x)|0\rangle$ as ...
-3
votes
0answers
17 views

X-rays-Is the mass of electrons being converted into energy? [on hold]

Are electrons converted into energy in an x-ray tube?
0
votes
0answers
28 views

Dynamic energy of capacitors in circuit

If I have 3 capacitors and 1 battery in a circuit how should I connect them in order to have maximum dynamic energy, when I connect them with the battery? Parallel or in series?
-3
votes
2answers
27 views

Can you pass cathode rays in a non vacuumed tube [on hold]

Is it possible to have a cathode ray discharge in a non vaccumed tube while having a low pressure?
0
votes
1answer
48 views

How does covering a hot bowl of soup prevent heat losses?

Recently I took out some soup to eat and got a call from a friend. I covered it with a plate and when i came back later, it was still hot. While i was eating, i wondered how does covering this hot ...
5
votes
1answer
81 views

Von Neumann entropy of mixtures of coherent states

I'm trying to calculate the Von Neumann entropy of statistical mixtures of coherent states. The problem is that such states are in general non-Gaussian, so one cannot follow the formalism developed ...
0
votes
0answers
23 views

Is it possible to get an analytic expression of the capacitance for this geometry?

Here is the geometry I'm talking about: Assume the red rectangle is at some constant potential V, like 10 Volts, and the blue is at ground. We can assume that the rectangles extend infinitely (to ...
0
votes
2answers
35 views

Balancing Orthogonal Forces on 2D plane with arbitrary placement [on hold]

I have a rectangular block in the xy plane with the center of mass that acts in the z direction at an arbitrary place in the plane. I also have 4 legs that support this weight underneath the block. ...
-2
votes
0answers
18 views

Non-zero spin meson have ever seen experimentally? [on hold]

Have been ever shown ( in experiment) none-zero spin meson? We should have it?
0
votes
1answer
17 views

Lens and Mirror Grinding

I am actually grinding my own lenses ( I am trying). Now I have been continuously using the chordal stroke for atleast 3 hours but i am unable to see any depreasion be it convex or conacve on the tool ...
0
votes
1answer
39 views

can the behavior of light be explained on the basis of a single theory?

Can the behavior of light be explained on the basis of a single theory ? example, wave theory of light ,if not then why?
0
votes
0answers
38 views

According to the theory of relativity, (relativistic) mass of an electron changes when it moves at very high speed; how and why? [duplicate]

It is given that $$ \mathbf m' = \frac{m}{\sqrt{1-\frac{v^2}{c^2}}} $$ How does (relativistic) mass change here?
2
votes
1answer
24 views

About series expansion of effective potential and its justification

The books on quantum field theory often uses an expansion of the effective action $\Gamma[\phi_c]$ in terms of $\phi_{cl}$ and its derivatives given by $$ \Gamma[\phi_c]=\int ...
-3
votes
0answers
178 views

Galactic binary engine found in the center of the Milky Way? [on hold]

It is accepted science that Sagittarius A* is the black hole in the middle of our galaxy, and motion measurements of Sag A* show that it is more or less stationary relative to our Sun, so why would ...
0
votes
0answers
8 views

Factors Effecting Neodymium Magnet's Grades and Strength?

Neodymium magnets have different grades in strength. Such as: N38, N45, N52... etc [ Where higher number means greater strength, in MGOe ] Since all magnets are made by saturating them in magnetic ...
0
votes
0answers
34 views

Determining the Lagrangian of a double pendulum [on hold]

Ok, I'm reading up on Lagrangian mechanics, and there is a problem that I don't really understand: the double pendulum (in this case, without a gravitational field). So, I want to take it step by step ...
3
votes
1answer
34 views

Physical limits to number of particles per collider bunch

Currently, colliders work with around $\sim\!10^{11}$ particles per colliding bunch. Recently LHC has increased this number to $10^{13}$. I would like to know if there are, in principle, physical ...
0
votes
0answers
16 views

torsion tensor proof [on hold]

I looked up torsion tensor derivation on 2 different books, and encountered 2 different situations, so my mind has been confused. For the first image, I could totally understand how torsion tensor was ...
0
votes
0answers
31 views

Klein Gordon, Dirac, Proca [on hold]

How do we know these equations : Klein-Gordon, Dirac, Proca is for spin 0, spin 1/2 , spin 1? How did people find Klein Gordon doesn't work for spin 1/2?
0
votes
2answers
24 views

Application of Bernoulli's equation to siphon

I'm trying to understand how to use Bernoulli's equation in practice. So I will make an example of where is my confusion. I found this great explanation on Wikipedia about the siphon, but there is a ...
0
votes
0answers
23 views

Finding viscosity of a liquid [on hold]

A ball bearing of diameter 10 mm is dropped into an oil of density 850 kgm–3. The ball bearing has a volume of 5.2 × 10^–7 m3 and density 7700 kgm–3. When the ball reaches terminal velocity ...
2
votes
0answers
27 views

Induced metric is a scalar for transformation from $x\to x'$? (Poisson E.A p.62)

I have a (simple) question about the induced metric $h_{ab}$. In Poisson E.A. (a relativist toolkit) it says in p. 62 that the induced metric $$h_{ab}=g_{{\alpha}{\beta}} \frac{\partial ...
0
votes
1answer
43 views

Which elementary particles have been seen up to now?

Which elementary particles have been shown up to now? which one except Graviton, haven't seen? I need an update one, I am searching but I couldn't find. If anyone could answer me, I am so thankful.
0
votes
0answers
10 views

Transverse momentum [duplicate]

I'm having an introduction on detector systems in particle physics. The sources I read constantly talk about the measurement of "transverse momentum". However, I cannot find a definition of what is ...
-1
votes
0answers
11 views

How do I decide what my x and y axes will be when given data on resistivity?

Ok so I have been given a table with 3 lots of information; the wire length, voltage, and current (and the cross-sectional area is also stated). It says to then determine the resistivity. I was ...
0
votes
3answers
22 views

Finding equivalent capacitance between A and B, [on hold]

Following is the question, asked is to find equivalent capacitance between A and B. I've tried couple of times and getting 7/3 micro farad as the answer while the correct answer is 8/3 micro farads. ...
-2
votes
0answers
19 views

How much pascals is needed to lift a human? [on hold]

I wanna ask you that how much psi is required to lift a man 1000 metres up in the sky of weight 'bout 100 kgs??? I'm not much good at physics
0
votes
1answer
26 views

Energy Transferred to a Spring by a Time Dependent Force (using Fourier Transformations)

I found an excersice in Byron-Fuller's: "Mathematics of Classical and Quantum Physics", about the energy which is transferred to a spring by a time depended force of the form: $F(t)=\left\{ ...
-4
votes
1answer
53 views

Is superposition state of SHO ever observed?

Feynman says, "It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong." So, is superposition state of Simple ...
0
votes
0answers
18 views

What's the conductivity of graphene nanostructres (nanoribbon, nanomesh)?

As we know, the conductivity of graphene can be expressed with Kubo formula,including intra transition and inter transition. But does graphene nanoribbon or graphene nanomesh have the same ...
7
votes
3answers
95 views

Validity of mean-field approximation

In mean-field approximation we replace the interaction term of the Hamiltonian by a term, which is quadratic in creation and annihilation operators. For example, in the case of the BCS theory, where ...
0
votes
0answers
6 views

Power scaling behavior in Detrended Fluctuation Analysis

I am trying to apply DFA in my time-series, however, remain the the determination linear relationship of the log fluctuation vs. log scale plot i.e. slope which indicates to the power scaling behavior ...
0
votes
2answers
21 views

Gamma spectroscopy - Nuclide identification

I have a question about what the usual practice is for nuclide identification in gamma spectroscopy. For example, if I see a line at 477 keV, I would write that the origin of this line is $^7Be$. As ...
-3
votes
0answers
36 views

Conservation of mechanical energy [on hold]

Think of a case where non-conservative force does positive work. In this case, my teacher said that mechanical energy will not change. But work done by non-conservative force = total final ...
2
votes
0answers
35 views

BCS Theory, Physics behind it

I am going through the mathematical steps of BCS Theory, but somehow I can't get the physics. What is the physics behind Bogoliubov transformation, how can I visualize what is happening there? Can ...
1
vote
0answers
16 views
0
votes
0answers
28 views

Light of planets and natural sattelites [on hold]

I have been getting stuck while solving and imagining the following problem: According to Plank's quantum theory "Energy radiated or absorbed by a body is not continuous but discontinuous in the form ...
2
votes
1answer
44 views

Physical interpretations of the generating functions $Z[J]$ and $W[J]$ (or $E[J]$)

In quantum field theory, the generator of all Green's functions $Z[J]$ and that of the connected Green's functions $E[J]$ are related as $$Z[J]=\exp[-iE[J]]=\int D\phi\exp[i\int ...
0
votes
0answers
26 views

How conclusive is “Gravitational red-shift Gedanken”?

The gedanken goes as you take a particle of mass $m$ at a height $H$. Then let it fall to gain the velocity (approximately)$\sqrt{2gH}$ when it reaches the ground. Convert the particle into a photon ...
1
vote
1answer
42 views

Bulbs in parallel/series (very basic) [on hold]

I need some help understanding very basic circuit concepts, specifically for the question in the image below. So from what I know is that in a series setup: voltage is divided over the components, ...

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