0
votes
0answers
2 views

What is the fraction of the incident intensity passing through polarized sheets?

Unpolarized light is incident on a set of three polarizing sheets as shown in the figure at right. The polarizing directions of the sheets make angles 10*, 55* and 85* to the vertical. what fraction ...
0
votes
0answers
2 views

Specific heat at constant volume

Me and my friend came across this derivation is some lecture notes of our thermal physics module. We have been trying to calculate the partial differential of the internal energy but cannot get the ...
0
votes
0answers
4 views

Would any interference maxima be missing in the double slit experiment?

An aperture in the form of a narrow slit of 0.9mm wide forms a diffraction pattern on a screen placed 6.0 meters away when illuminated with light of wavelength 600 nm; would any of the interference ...
0
votes
0answers
6 views

Amplitude of electric field produced by satellite dish

A telecommunications satellite is in geostationary orbit and it has a 1 m transmitting dish optimised for coverage of Europe. If the output power from this dish is 100 W, very roughly estimate the ...
0
votes
0answers
7 views

Contradiction (?): DNA ion mobility vs diffusion constant

There is a certain confusion about DNA ion mobility and diffusion constant in the literature. Consider double-stranded DNA ions in pure water. DNA ions are negatively charged due to phosphoric acid ...
3
votes
1answer
104 views

What is the difference between Chiral anomaly, ABJ anomaly, and Axial anomaly?

I get confuse with these three terms: Chiral anomaly, ABJ anomaly, and Axial anomaly. I can not find standard definition of these three. Is there anyone can describe precisely?
1
vote
1answer
32 views

What is the procedure to follow if I want to renormalize a given operator $\cal{O}$ or a given coupling?

Consider QED. I know that the renormalization constant of the mass can be obtained from considering the electron propagator, regularizing it and renormalizing it. I know that from this process we can ...
0
votes
0answers
7 views

Why is the shadow of a wind turbine a bit slow at first then very quickly, etc. and not equivalent to the wings?

When I stand at a wind turbine and look at the shadow on the ground, the shadow is a bit slow at first then very quickly, etc. Very strange.
2
votes
0answers
11 views

How exactly analyticity of S-matrix comes from causality principle?

Recently I've read that analyticity of S-matrix ($S(k)$, where $k$ corresponds to momentum, may be analytically extended into complex values of momentum) comes from causality principle. How to prove ...
0
votes
0answers
9 views

Why air conditioner, dehumidifier, and heater all can lower the relative humidity?

I think so far I understand it this way: why is humidity in Asia 75%, and humidity in California 82%, but California feels dry, and Asia feels humid. It is because there is something called Dew ...
0
votes
0answers
6 views

Relation of current with frequency and voltage

I tried to solve a numerical problem but I got stuck and I think it very necessary I will drwa certain basic conclusions when I would found its solution. The question is: An incandescent lamp takes ...
0
votes
0answers
4 views

Derivation of impedance matching formula

When matching impedances with a quarter wavelength coupler, how do I derive that its impedance has to be $$ Z_2=\sqrt{Z_1 Z_3} $$ where $Z_1,Z_3$ are the impedances of the adjacent materials?
2
votes
2answers
408 views

Finding the illuminance from a triangular light source

Since most light sources in games are point-like, it's pretty difficult to approximate area light sources with point sources. As triangles are a universal form to represent 3D models (thus area light ...
2
votes
1answer
195 views

Mean field theory Weiss Approximation for the Isling Model of a Protein

A model for protein in 2D can be formed by adding bonds of fixed length $l\sqrt{2}$ on a square lattice along the diagonal, ie $\hat{\mathbf{b}}_i=\frac{1}{\sqrt{2}}(\pm \hat{\mathbf{x}}\pm ...
0
votes
1answer
48 views

Solving the Three-body problem numerically

I want to create a program in $Mathematica$ that solves numerically the Three-body problem by Euler-Lagrange's equations. I was searching some methods to sucessfully do it. So I found a way to solve ...
0
votes
0answers
9 views

Decomposition of a tensor under transformations

To illustrate my question I'll take an example from theory of relativity: An arbitrary 4-tensor $A^{ik}$ changes under a general coordinate transformation: $$ A'^{ik} = C^{i}_mC^{k}_n A^{mn} $$ ...
1
vote
1answer
21 views

Is event horizon absolute to all observers?

Recently I had discussion whether the event horizon of a black hole is absolute or relative to different (outside) observers. Does someone just 1m above the horizon perceive it at the same depth as ...
0
votes
0answers
7 views

Calculating work needed to move a charge between plates of an uncharged capacitor

My first guess was zero work because there's no electric field(I think). E.g. a parallel-plate capacitor $4.9 cm$ on a side, spaced $1.0mm$. The work needed to move $6.8\mu C$ seems to be $1.1J$ And ...
8
votes
3answers
516 views

Why do rainbows have distinct colors?

When I searched on the Internet for the reason of formation of rainbows, I got many explanations like this one & this. All the explanations consider only one spherical water droplet (like this ...
0
votes
1answer
22 views

The proof of a discrete Fourier identity in quantum field theory

On page 25, in the book Quantum Field Theory for the Gifted Amateur by Tom Lancaster and Stephen. J Blundell, it states the following: We impose periodic boundary conditions forcing ...
0
votes
1answer
101 views

In a CMCS 2-body system, why does the speed of the particles after collision stay the same?

A particle $m_1$ is traveling with velocity $v$ toward a stationary particle $m_2$. The velocity of the center of mass is given as $v_c=\frac{m_1}{m_1+m_2}v$. Changing to a moving coordinate system, ...
0
votes
0answers
19 views

Travelling at a relative speed greater than the speed of light

I've wondered about this since I was a kid. I've been told the speed of light is a constant (c), which would mean that light always travels at the same velocity. ...
0
votes
1answer
22 views

Oberving a photon through double slits

If we send a particle with mass through the double slits we observe a interference pattern. That is of course if we don't observe which slit the particle goes through. If we do then we get two peaks ...
0
votes
0answers
9 views

EW phase transition and baryogenesis

There are three Sakharov conditions of baryogenesis: CP symmetry violation. Baryon number conservation violation. Thermodynamical equilibrium violation. In SM the first one is satisfied by CKM ...
0
votes
0answers
14 views
1
vote
2answers
68 views

Conservation of angular momentum - exercise

A sphere of mass $M$ is rotating with constant $w_0$ regarding the axis that intersects the north and south pole of the sphere. A bug of mass $m$ sits on the north pole and starts to walk along a ...
2
votes
0answers
10 views

Size of a glass capillary for noticable capillary action

How big would a glass capillary have to be to have noticable capillary action? Also, does capillary action happen in plastic tubes?
4
votes
3answers
288 views

Can I do something for being heavier to be lifted?

Playing with a friend, one started to try to lift the other, and then the other way back. We started to talk about "making some force" to be more difficult to lift - one could think about having more ...
1
vote
0answers
47 views

What's the advantage of using bra-ket notation over inner-product notation? [migrated]

Both notations look pretty similar, and appear similar when undergo algebraic operations. Apart from personal taste (aesthetics) concerning commas (<,>) vs. pipes (<|>), what is (are) the ...
1
vote
2answers
80 views

Silicone tube with three holes, flow rate, pressure

I have a silicone tube -- a saline solution flows in from one end, and then flows out of three holes of equal diameter and equal distance from each other that are along the side of the tube. What can ...
0
votes
1answer
41 views

Two isobars they differ in binding energy, will they differ in radius as well?

It is a problem from introduction to nuclear physics- by krane, chapter: nuclear properties, problem 7. It goes like this: From the known masses of $_{~~8} ^{15}\rm O$ and $_{~~7}^{15}\rm N$, compute ...
33
votes
4answers
4k views

Do rainbows have ultraviolet bands and infrared bands?

We have seen that rainbows looks so colorful as we are only able to see the visible light only. Do they also have ultraviolet bands and infra-red bands, that we are unable to see? I know someone has ...
3
votes
4answers
274 views

Surface charge density for an off-centre charge in a spherical shell?

How would I evaluate the surface charge density on the inner and outer surface of a neutral, spherical, conducting shell which has an off-centre charge $q$ inside? I believe that we can not use the ...
6
votes
2answers
130 views

What is the exact meaning of homogeneity in cosmology?

I understand that, in general, homogeneity is the physical attribute of being uniform in composition (" of the same form at every point"), but I'm slightly confused when it is used in cosmology as ...
3
votes
5answers
222 views

Does coordinate time have physical meaning?

I have always been a little confused by the meaning of the "$t$" which appears in spacetime intervals or metrics in general relativity. I concluded that $t$ was just a mathematical thing which allow ...
2
votes
3answers
79 views

Violation of conservation of energy?

Imagine a perfectly spherical mirror with 100% reflection. Imagine a point source of light in the center. The point source keeps radiating light. Will the light undergo destructive interference ...
0
votes
1answer
10 views

Why can insulators be charged by friction but not by conduction?

When you charge an insulator by friction, the close contact of two electron clouds (each from a different medium) allows for electrons to be transferred between them. Yet why can the same not be ...
1
vote
2answers
65 views

How does this youtube video demonstrate quantum entanglement? [on hold]

The following is an experiment that shows "spooky action at a distance" of quantum entanglement; that is, when we measure some properties of two entangled photons, we find that measuring property of ...
0
votes
1answer
20 views

time dilation :-

In the time dilation equation $t'=t/\sqrt{1-(v/c)^2}$ where $ t'$ is the time measured by an observer in motion for the same event, where $t$ is time measured by the observer at rest. Imagine a ...
0
votes
0answers
16 views

waves particle duality of human body

De Broglie stated electrons can travel as particles and waves. Electrons show its waves properties when they can diffract through a carbon layer. So, I am not sure about his statement which human also ...
0
votes
0answers
87 views

Alignment of Fermi Levels between Metal and Insulator

If I stick a metal and insulator together, will the Fermi level of the metal align with the insulator? When people draw a band diagram for a metal-oxide-semiconductor heterostructure, I never see ...
0
votes
2answers
1k views

How do Zener diodes work?

I was going through some of the theory behind Zener diodes. I know what they're used to work at constant voltage, but I don't know how they work. Actually, I kind of get that too, I know that voltage ...
9
votes
4answers
310 views

Seeking a quality plain-language description of the Wigner-Eckart theorem

I'm a third year physics undergrad with a very cursory knowledge of quantum mechanics and the formalism involved. For instance, I understand roughly how tensors work and what it means for a tensor to ...
3
votes
1answer
4k views

Charge inside conductor

I know that the $E$ field inside a conductor is zero. What happens if I put a source of charge inside the conductor? Say the conductor was spherical centered on the origin and there exists a charge ...
0
votes
1answer
23 views

Where does the Higgs Boson fit in the three generations of charged particle?

I am reading a book called "Gauge Fields, Knots and Gravity" by Baez et. al. In the first chapter, the authors explains that there are three generations of charged particles: First: electrons, ...
0
votes
1answer
19 views

Can a proton be trapped by eight other protons?

Q: Eight protons are permanently fixed on the corners of a cube. There's a ninth proton floating at the centre of the cube. Is there an escape for the proton or is it trapped? Justify with a ...
1
vote
1answer
2k views

Why is the mechanical advantage of a wedge = length of slope/ width?

Mechanical advantage is defined as Force Output/Force Input For a symmetrical wedge with the length of the slopes being equal and the width being the distance between the end points, the articles ...
0
votes
2answers
20 views

Best coordinate system for Projectile motion

What is the best coordinate system for describing the projectile motion? Rectangular coordinate system or n-t(normal and tangential) coordinate system.
0
votes
0answers
10 views

Modeling $k$-logistic diffusion process

I'm trying to model a diffusion process characterized by subsequent logistic diffusion processes. To give a better idea of what I'm trying to model, you can take a look at the attached figure. In such ...
0
votes
0answers
4 views

Frank-Hertz experiment what transition takes place?

For the Frank-Hertz experiment there is a voltage drop at $4.9V$ what transition does this represent in the mercury? Looking at the energy levels it seems to be from the ground to the 2nd excited ...

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