-1
votes
0answers
9 views

Transition Capacitance & Diffusion capacitance of a diode

What are Transition and Diffusion Capacitances of a Diode? Why is Transition capacitance more significant in the reverse bias condition? Why is Diffusion Capacitance more significant in the forward ...
3
votes
1answer
61 views

Would a Theory of Everything allow us to calculate the constants of physics?

I have heard several times in the past that a Theory of Everything would allow us to calculate (as opposed to measure) the fundamental dimensionless physical constants. What I mean is, e.g., the fine ...
1
vote
2answers
60 views

Would condensed matter physicists need more than three dimensional calculus?

The difference between "multivariable" and "vector" calculus, as stated on Yale's website, is that multivariable would only go through 2 or 3 dimensions, and so would rely heavily on geometric ...
1
vote
0answers
22 views

How does Huygens Principle incorporate the unidirectional property of a traveling wave?

I was reading French's Vibrations & Waves where he discusses Huygens-Frensel Principle. The principle talks about how secondary sources give rise to secondary wavelets to form the displaced ...
1
vote
1answer
38 views

Time Dilation In Between Two Objects

Suppose an object A is exactly halfway in between two identical objects B and C, so the magnitude of the cumulative acceleration on object A is $0$. Objects A, B, and C have no velocity relative to ...
5
votes
5answers
86 views

How can we explain the difference in change of kinetic energy, due to different frames of reference?

Imagine a ball ($m= 1\,{\rm kg}$) moving at a velocity $2\,{\rm m}/{\rm s}$ towards a wall. When it hits the wall, it suddenly stops, thereby liberating all its ${\rm KE}$ as heat. Here, the initial ...
-1
votes
1answer
25 views

How can I estimate CO2 emissions for a vehicle travel distance

How can I properly estimate CO2 emissions for a given travel distance (of a private vehicle)? I found the following formula, but I'm not sure that it's correct: ...
2
votes
1answer
33 views

Difference between symmetry and invariance

I'm wondering what's the real difference between symmetry and invariance in Physics. I believe that sometimes the two words are given the same meaning and some other times they are used in a different ...
0
votes
0answers
16 views

Using stellar spectroscopy to measure stellar parameters, why is it log g?

Stellar spectroscopy can in principle measure the stellar surface gravity, radii, effective temperature, and stellar rotation. Why is it that surface gravity g is ...
0
votes
0answers
20 views

Free fall and gravitational time dilation

An observer 'A' at rest in a gravitational field has some amount of time dilation relative to an observer 'B' far away from the gravitational field. Would the clock of an observer 'C' in free fall at ...
-1
votes
1answer
19 views

What if electric force was independent of the distance?

The electric force between two charged particles becomes weaker with increasing distance. Suppose instead that the electric force were independent of distance. In this case, would a charged comb ...
-6
votes
0answers
42 views

how to solve the following question about quantum mechanical wave function? [on hold]

How to solve this question regarding quantum mechanical wavefunction ?
0
votes
1answer
12 views

Are the produced entangled photons in type II SPDC always in phase?

Are the produced entangled photons in type II SPDC (spontaneous parametric down conversion) always in phase? In Kim's delayed choice quantum eraser, two entangled photons are produced by a BBQ ...
0
votes
1answer
42 views

Does spaghettification really happen with conditions found close to a black hole?

This website tries to explain why the term spaghettification doesn't actually occur when something gets close to a black hole. The argument of the author is that the equations we use to predict the ...
1
vote
3answers
51 views

Why does a sheet of paper fall slower than the same when rolled into a ball?

It depends on volume but both the sheet and the sphere have the same volume.Does surface area play any role here?
-1
votes
1answer
32 views

Photon energies and attenuation

I hope you can help. I am trying to understand which attenuation effect (photoelectric, compton scatter and pair production) is dominant at which level of photon energy and why. The levels are 10keV, ...
0
votes
0answers
15 views

Nucleon-meson interaction

Suppose interaction lagrangian between neutron-proton doublet and $\pi$-mesons: $$ \tag 1 L_{\pi pn} = \bar{\Psi}\pi_{a}\tau_{a}(A\gamma_{5} + B)\Psi , \quad \Psi = \begin{pmatrix} p \\ n\end{pmatrix} ...
10
votes
2answers
820 views

Why don't photons split up into multiple lower energy versions of themselves?

A photon could spontaneously split up into two or more versions of itself and all the conservation laws I'm aware of would not be violated by this process. I've given this some thought, and a system ...
2
votes
1answer
38 views

Derivation of geodesic deviation equation from two neighbouring geodesics

I'm stuck trying to follow Foster and Nightingale's derivation of the geodesic equation from two neighbouring geodesics $x^{a}\left(u\right)$ and $\tilde{x}^{a}\left(u\right)$ joined by a ...
-1
votes
1answer
26 views

Time taken for sliding mass to fall down

Figure shows a small block of mass m kept at the left end of a larger block of mass M and length l. The system can slide on a horizontal road. The system is started towards right with an intial ...
0
votes
1answer
25 views

Thermal expansion of metal spring

I am attempting to figure out why a laser layout tool I have is drifting over time. It was designed with a small adjustment mechanism that relies on a spring to apply pressure to a fulcrum that ...
1
vote
0answers
49 views

Poisson brackets and magnetic field [on hold]

I'm a maths student trying to teach myself some physics so sorry if I'm missing something simple here. I think the main problem is lack of experience with the Levi-Cevita symbol. We have a particle ...
-1
votes
1answer
18 views

Statics Vector Question [on hold]

I need help with this problem image of problem: http://postimg.org/image/87o0tyfyp/ I could answer the question if I had a second angle but I don't even know where to begin to solve the question. ...
1
vote
0answers
20 views

Superconductivity: how does the critical temperature depend on the pressure?

This question is inspired by a recent publication, in which researchers managed to boost the record critical temperature at which a substance becomes superconducting by applying an enormous pressure ...
4
votes
1answer
118 views

Using a laser to overhear a room conversation

Movies with science based tricks and gimmicks are generally silly and sometimes even annoying. The science based trick that I don't know enough about to judge is the following (and I have seen it in a ...
0
votes
0answers
27 views

Difficulty in understanding Maxwell Boltzmann distribution in case on ions in a field

I learned that the velocity of molecules obey Maxwell Boltzmann (MB) distribution at a Temperature T. If I have ions of mass 'M' accelerated to 2eV in a specific region. As the ions are not ...
0
votes
0answers
27 views

change in free energy at natural state

I am styding a book on thermoelasticity, here free energy $f(e_{ij},T)$ is expended into taylor series in the vicinity of the natural state (when $e_{ij}=0$,$T=T_0$) and entropy s such that ...
0
votes
1answer
55 views

Children of entangled particles

Theres a photo on the wikipedia page Quantum Entanglement there's a image of a photon being split into two entangled photons via crystal. I used this picture to demonstrate the scenario below. ...
0
votes
0answers
3 views

redistribution of charge between plates

How is charge redistributed when a charged conducting plate is placed between two identical wire-connected uncharged plates?
0
votes
1answer
53 views

is there an operator which measures the mass of particles?

When I studied a spin, the textbook said spin is an intrinsic quantity like mass. However, while we can calculate just expectation values $ \langle \textrm{S}^2\rangle $ or $ \langle S_z\rangle $, the ...
0
votes
0answers
31 views

QED+Classical Background Renormalization

I would like to ask a question related to quantum corrections and renormalization in QED. We have the QED vertex $\overline{\psi}[-ie \gamma^{\mu}(B_{\mu}+A_{\mu})]\psi,$ being $B_{\mu}$ a classical ...
0
votes
2answers
34 views

Reflection during refraction

I have observed in a book (one that is different from the one that I study with in school) that a light ray reflects during refraction, which is a partial reflection, but when does that occur? Is it ...
2
votes
0answers
24 views

Definition of luminescence

I saw a definition of luminescence as "any light not resulting from blackbody radiation", but in my view it's too broad. Is an accelerating electron producing luminescence? Or an electron recombining ...
0
votes
0answers
17 views

Electric field radiation with moving charge and observation point

I've been working on Chapter 34 of the first volume of the Feynman Lectures on Physics http://www.feynmanlectures.caltech.edu/I_34.html#Ch34-S1. In Fig. 34–3 (reproduced above) Prof. Feynman shows ...
-5
votes
1answer
38 views

difference between mass and weight [duplicate]

I already know that when I standing on weighing machine it's measuring my mass not my weight, but when I take the same machine to moon it's will read different value. according to my information that ...
-6
votes
2answers
64 views

Natural Philosophy [on hold]

My question is an extension of the celebrated question on the moon’s existence if unobserved. “do we still have tides on earth if the moon is unobserved?”
0
votes
3answers
61 views

What was the motivation behind the work formula?

Surely there must be a reason we decided to use this as a metric for mechanical energy.How was it developed and what made it more acceptable than other work formula candidates (Like force over time, ...
2
votes
1answer
49 views

Can a static electric field have a vector potential field?

We know very well that static electric fields have scalar potential fields, and magnetic fields can't have scalar fields, as $$\nabla\times \vec{B}=\mu_0\vec J$$ $$\Rightarrow \int\nabla\times ...
0
votes
1answer
25 views

One stupid question about Dirac mass term and grassmannian numbers

Let's have Dirac mass term in lagrangian: $$ L_{M} = \bar{\Psi}\Psi $$ Lagrangian must be real-valued, i.e., its hermitian conjugation doesn't change it. But due to grassmannian nature of spinor ...
1
vote
0answers
30 views

Show that the boundary layers diffuse out from the plate with speed $\sqrt{\frac{\nu}{t}}$

I was wondering if somebody would be able to help me with this problem. I know how to solve it using dimension arguments but I'm unsure what is meant by transformation techniques. Any help would be ...
1
vote
1answer
15 views

What justifies adding phasors' vertical components

I learned that, when superimposing two waves on top of each other to calculate the resulting wave's amplitude, it's helpful to use phasors. From what I gathered, phasors are vectors originating at the ...
0
votes
1answer
28 views

How does rainbow stay for such long time even it is caused due to raindrops?

Rainbow forms when light rays pass through a raindrop (usually, it can be a watet droplet also) and it undergoes several phenomenon like refraction , reflection , dispersion , But after the rainbow is ...
1
vote
1answer
59 views

Can an electron go along different paths at once in a circuit

A single electron moves along a circuit and comes to a fork in the wires. The wires separate but come back together near the end of the circuit. From what I know, the electron will travel along all ...
-2
votes
1answer
40 views

Could the Big Bang have simply been two black holes hitting each other at 99% of the speed of light? [on hold]

Given two equally massive black holes moving at 99% of light speed, it seems there would clearly be enough energy for most (99%?) of the mass of both to be ejected and / or radiated well beyond the ...
1
vote
1answer
50 views

Can one detect a single photon through measuring its impulse/momentum on a mirror?

Can one detect a single photon through measuring its impulse/momentum on a mirror? If the answer if YES or theoretically possible, photon path and interference fringes can be detected simultaneously ...
0
votes
2answers
28 views

Why does electrostatic energy not obey superposition principle? What does the extra energy term account for?

Energy stored in an electrostatic field is given by $\frac{\epsilon_0}{2}\int\text{E}^2\text{d}\tau$ where the integration is over all space.If $\vec{\text{E}_0}=\vec{\text{E}_1}+\vec{\text{E}_2}$ and ...
-1
votes
2answers
40 views

why we can't see light emitted from tv remote while a camera can?

If we try to see light emitted from tv remote we can see this.while if we try same in camera we are able to see this. Why
2
votes
0answers
18 views

What is the pressure equation of an ionized gas?

I have $N$ ${\rm H}^+$ gas molecules in a sealed, electrically insulated container. What equation can I use to accurately calculate the pressure of the gas? It seems to me that $PV = nRT$ will not ...
0
votes
0answers
22 views

How M theory or String theory explains fundamental forces and Quantum mechanical phenomena? [on hold]

How M theory explains fundamental forces gravity,strong,weak and electromagnetic? And how does M theory explains phenomena of light like reflection,refraction,diffraction,interference etc?
0
votes
0answers
10 views

Question related to charged concentric conducting shells

There is a charged conducting spherical shell given a certain positive charge.Another larger spherical shell is given the same negative charge.The first shell is now placed inside the second shell so ...

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