# All Questions

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

How to solve this question regarding quantum mechanical wavefunction ?
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### 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 ...
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### 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 ...
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### 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?
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### 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, ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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
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### 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 ...