0
votes
0answers
19 views

Higher $L$ lower energy?

For multi-electron atoms, what is the physical reason behind the fact that a higher total orbital angular momentum, $L$ gives a smaller total energy, $E$?
0
votes
0answers
7 views

Decay kinematics of Higgs boson

So I'm looking at a two-body decay question for the $h\rightarrow\gamma\gamma$ decay channel for the Higgs Boson. I am asked to find the invariant mass of the Higgs boson. I'm not too sure how to ...
9
votes
2answers
136 views

Spatial coherence of SLED light (width of active region?)

As far as I know, super-luminescent diodes (a.k.a. SLEDs) have a very similar structure to laser diodes, except that the front faces of the active region are tilted to prevent the sort of reflections ...
0
votes
0answers
12 views

Rogers-Ramanujan and integrable systems

I'd like to understand the underlying geometry of the Rogers-Ramanujan continued fraction from the point of view of integrable systems (ideally Toda type theories). The generating function ...
0
votes
1answer
13 views

Relationship between fracture of solid plates and its curvature

I do some school projects about fracture of glass, my assumption is this phenomenon related to the curvature of these plates, specifically, fracture starts from the point which is having “maximum” ...
1
vote
2answers
28 views

Motivation for usage of 4-vectors in special relativity

I understand that if one considers a 4-dimensional space-time from the outset then 4-vectors are the natural quantities to consider (as opposed to 3-vectors as in Newtonian mechanics), since the ...
0
votes
0answers
12 views

Which way does the force due to current point

The current is towards the right. The particle with charge $-q$ is going with velocity towards the right. How does one find the force due to the current on $-q$? (The RHR doesn't do anything here). ...
0
votes
0answers
13 views

Current scientific knowledge of antimatter [on hold]

I am currently working on a theory and need to know something. How much do scientists know about antimatter? About it's properties, charges, location in the universe, etc. If this question will ...
8
votes
2answers
386 views

Why was the Stark effect discovered much later than the Zeeman effect?

This is strange. The Zeeman effect involves the magnetic field. The Stark effect involves the electric field. In the course of classical electrodynamics, we get the impression that for many physical ...
9
votes
2answers
726 views

Do stars remain electrically neutral? [duplicate]

How electrically neutral do stars remain through their lifetime? As an example, I could imagine processes such as coronal mass ejections leaving the Sun in a slightly charged state. Are there such ...
1
vote
0answers
7 views

Why do $C_p$, $\alpha$ and $\kappa_T$ all approach to infinity when two phases coexist at the mean time?

My textbook (writed by Chinese) says that when two phases of a system coexist at the same time, this system's isobaric thermal capacity $C_p=T(\frac{\partial S}{\partial T})_p$, coefficient of ...
0
votes
0answers
6 views

Question pertaining to the branching ratio of Ka0ns

I'm a little lost for part c of this question: I understand the $\mathcal{BR}$ (branching ratio) for species $i$ is $\mathcal{BR}=\Gamma_{i}/\Gamma_{T}$ (total Decay width). I know that ...
3
votes
1answer
312 views

Drag - Dimensional Analysis / Buckingham Pi

Dimensional Analysis / Buckingham Pi Theorem I'm working on dimensional analysis and I'm having trouble. Here's a problem from my book I'm working on for practice. I'm suppose to consider a small ...
0
votes
1answer
27 views

Does the electrons in Stern-Gerlach aplliance change their energies and how?

When an electron goes thru a Stern-Gerlach appliance it changes its spin projection. Then there must be a change of energy content of the electron due to this event. But it is also known that magnetic ...
1
vote
0answers
20 views

Finding the exponent of $\lambda$ in Wien's displacement law

I am reading this paper on a short history of the $T^4$ radiation law. In particular, on page 5, By assuming that the wavelength of radiation emitted by a molecule was a function only of its ...
-1
votes
1answer
24 views
-1
votes
1answer
30 views

How do I get the maximum EMF in this problem? [on hold]

Concern is often expressed regarding the potential adverse effects of oscillating electric and magnetic fields on the human body. Consider a typical magnetic field created by mechanical ...
2
votes
2answers
522 views

Is there an equation to calculate efficiency of an optical fiber to transmit sunlight for length of 4 m

I want to transmit sunlight over a distance of approx 4 m via optical fiber. Ideally I want to light up the whole house with sunlight. I was reading that the largest diameter for an optical fiber may ...
2
votes
1answer
257 views

Electric field in space created by intersection of spheres of charge

I am trying to calculate the electric field in space created by a body assembled by the intersection of 2 spheres. The upper sphere, its center is at $$\frac{d}{2}\mathbf{\hat{z}}$$ with radius $R$ ...
0
votes
0answers
31 views

Blue bird physics- Angry Bird

This is a question from my assignment which is Angry Bird related. Here it is: Before designing new types of birds for the Grumpy Birds game, you are asked to first verify the design of one of ...
2
votes
1answer
36 views

Does the human body have a measurable gravitational field?

I am researching communication other than speech or vision. The human body emits radiation in the form of heat; As the body has mass, will it have a gravitational field?
-1
votes
0answers
6 views

Heating during expansion in Joule Thomson - Mechanism?

When a real gas(like H2,He) expands through a porous plug into free space, they heat up. How? How does it get the extra energy?
0
votes
0answers
11 views

Magnetic dipole moment aligning with external field

Is there a law governing the tendency for the magnetic dipole moment to align with an external magnetic field? If you look at the classical model of an electron orbiting a nucleus, Fleming's Left Hand ...
0
votes
1answer
39 views

Can drag force and lift force be in the same direction in the following case?

In the attached picture, can I say that there is a lift force in the Y-direction, and a drag force too in the same Y-direction? $F_L$ proportional to $V_fx^2$ ? $F_D$ proportional to $V_py^2$ ? Is ...
0
votes
1answer
28 views

How commutators reverse the direction of current?

I've seen this video and read this article about commutators but I still couldn't get how commutators reverse the direction of current.I would like an simple and intuitive answer.
0
votes
1answer
106 views

Is 0.1 bar (hydrostatic pressure) equivalent to 0.1 bar vacuum pressure (absolute pressure)?

Suppose we would like to test the ability of an objec to withstand the pressure under 1 meter of whater. I would like to understand how to simulate this situation using vacuum. Is the 0.1 bar (for 1 ...
3
votes
2answers
482 views

Simplest explanation of pendulum having a constant time period at low angles

What is the simplest explanation for the pendulum having a constant time period at low angles?
0
votes
1answer
34 views

Thermodynamics - Change in temperature based on time

Hello Physics Stack Exchange, This is my first post on this forum, please correct me on any semantic mistakes I may make. Recently in my physics class we did a lab on Heat Capacity, where we had a ...
-1
votes
0answers
12 views

Could dark energy and particles create magnetic field? [on hold]

Could dark energy create magnetic fields or is this just quintessence theory?
0
votes
0answers
6 views

Optimum “fur” dimensions for absorbing ultrasound at a given wavelength?

By "fur" I mean an array of bendable fibres aligned vertically on a substrate. The ultrasound hits it at an oblique angle. Is there a spacing that will provide optimum absorption? A basic thought ...
0
votes
0answers
7 views

Electromagnetism question involving magnets on the ends of a metal pole

My teacher showed us a phenomenon in school involving a metal pole with two magnets on each end. The magnets are aligned so that both south poles are stuck to each end of the metal pole. This results ...
-1
votes
0answers
12 views

Invariant amplitude in QED in terms of Mandelstam variables

So I'm having a little trouble with this question: These are my workings thus far: I just can't seem to get certain terms to vanish. I have the 1/4 factor for going between $8e^4$ to $2e^4$. Is ...
1
vote
1answer
33 views

Writing operator evolution as a quantum dynamical map

In the Heisenberg picture we have the evolution of the operator in time given by: $$A(t)=U^+A(0)U$$ I was looking into the theory of open quantum systems where we introduce the concept of a quantum ...
0
votes
0answers
12 views

Binocular vs. monocular field of view in head-up displays

I've been reading about head-up displays in Wiki: Head-up display and understand that it works such that an image from an LCD screen (automotive) or from a cathode ray tube (aviation) is projected to ...
0
votes
1answer
14 views

The effect of an electric field on capacitance

Decreasing the distance between the two parallel plates of a capacitor increases the amount of charge that can be held on each plate. If this is because the charges are attracted to each other and ...
5
votes
2answers
97 views
+50

Why don't we call the fermions in the standard model force carriers?

Maybe this is a chicken-and-egg problem, but couldn't we call all the bosons fundamental and treat the fermions as force carriers between them? EDIT: After all we never see the asymptotic states of ...
0
votes
0answers
6 views

Does the dispertion medium affects Quantum Dots fluorescence efficiency?

I would like to use CdTe Quantum Dots to make a fluorescent coating on a transparent support. There's a link to the material here: ...
0
votes
0answers
12 views
-2
votes
0answers
33 views

Diffraction and wavelength [duplicate]

Why is it that when the slit-width is much larger compared to the wavelength of light, there is little diffraction or spreading-out of the light? And why is it that the diffraction effects are ...
0
votes
0answers
19 views

Will the force acting be doubled? [duplicate]

If me and a man are holding a string, and I apply a force of 100N, the tension in the string would be 100N, and it would exert a 100N force on the man and an equal and opposite force of 100N on me. ...
0
votes
1answer
120 views

Confused regarding sign convention of silvered plano convex lens

I'm totally confused while finding the sign convention of a silvered plano convex lens. I know that equivalent power of such a system can be found by adding the power of the mirror and twice the power ...
0
votes
2answers
28 views

Maxwell's area construction, why?

In the standard derivation of Maxwell's area construction (which can be found on page 4 of this pdf) the following equation is often written: $$G(p_1,T)=G(p_0,T)+\int^{p_1}_{p_0}Vdp $$ When the two ...
2
votes
3answers
49 views

Deriving the field equations of a given action

Provided an action: $$S[A_\nu] = \int\left(\frac{1}{4}(A_{\gamma,\mu}-A_{\mu,\gamma})(A_{\zeta,\alpha}-A_{\alpha,\zeta})\eta^{\gamma\zeta}\eta^{\mu\alpha}+\frac{1}{2}\nu^2A_\mu A_\gamma -\beta A_\mu ...
0
votes
0answers
15 views

Why is the energy shift due to a 'sagging' potential negative and independent of box size?

Consider a box of width $L$ and the composed of the following potential $$V(x)=V_0x(x-L), x\in[0,L]$$ and $V(x)=\infty$ elsewhere. Using perturbation theory - with a square box as the similar ...
1
vote
1answer
22 views

Difference between dielectric and insulators

AS per my knowledge - dielectric are insulators which can be polarized in presence of external electric field. Does that mean all Insulators are not dielectrics ? If yes then kindly share example of ...
2
votes
1answer
332 views

Time-reversed twin paradox

This started with wondering about the nature of certain physical quantities under time-reversal - chiefly, that acceleration retains its magnitude and direction at a given time regardless of the ...
0
votes
1answer
44 views

Understanding work with rotational momentum/moment of inertia

Apologies for the basic question but between the vectors and the spinning, I'm getting confused. If I have a wheel with moment of inertia $I$ spinning at some rate $\vec\omega$ around an axis, what ...
0
votes
0answers
39 views

Can time $t$ be a space-like coordinate? [on hold]

In Minkowski coordinate system time work as time-like coordinate and $r$ a space-like coordinate. But inside event horizon of black hole both exchange their characteristic. Is that possible that in ...
0
votes
1answer
158 views

Why does the equation for effectiveness of heat exchangers have $C_{\text{min}}$ in the denominator?

For an ideal heat exchanger of infinite length, $$ Q_{max}=m_{h}C_{h}\left[T_{h,i}-T_{o}\right]=m_{c}C_{c}\left[T_{o}-T_{c,i}\right] $$ \begin{eqnarray*} m_{h}C_{h}T_{h,i}+m_{c}C_{c}T_{c,i} & ...

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