All Questions
3
votes
2answers
72 views
Is light's path a wave?
In a lot of textbooks I see a schematic of light drawn as a squiggly line. I have even heard that some things are too small to be seen because they are smaller than the wavelength of light (and ...
4
votes
1answer
50 views
Bunsen Burners and the Sun
Why do Bunsen burners burn blue in the center? What element is being burned?
Why does the sun glow yellow, and not blue-a Bunsen burner is much cooler and yet it burns blue. Is it because the ...
4
votes
1answer
58 views
Peculiar Hamiltonian Phase space
I was solving an exercise of classical mechanics :
Consider the following hamiltonian
$H(p,q,t) = \frac{p^2}{2m} + \lambda pq + \frac{1}{2}m\lambda^2\frac{q^6}{q^4+\alpha^4}$
Where ...
1
vote
2answers
42 views
Different batteries connected in parallel
If we have 2 batteries one of emf x and the other is of emf y and we connect them in series we get an effective emf of x+y.
But what if we connect them in parallel, how to calculate the emf now?
2
votes
1answer
66 views
Bleaching groundstate
I'm reading an article about two-dimensional infrared spectroscopy and I don't understand the following sentence.
Bleach or stimulated emission contributions yield negative signals.
What are ...
1
vote
1answer
58 views
Assuming space is infinite can our observable universe be an island amongst an archipelego?
According to recent measurements our observable universe is roughly 93 billion light years in diameter; also it appears (according to WMAP measurements) that spacetime is flat.
Supposing space is ...
1
vote
0answers
38 views
Why is the angle of impact complementary to the angle of launch in the simple equations for the range of a projectile?
I'm using the standard equation for the range of a projectile:
\begin{align}
d &= \frac{v\ \text{cos}\theta}{g} \left( v\ \text{sin}\theta + \sqrt{v^2\ \text{sin}^2\theta + 2gy_0}\right)
...
-4
votes
1answer
80 views
Describing physical constants in alternate wording; c = there can only be 671million miles of space for every second of time [closed]
This spawns from part of an answer to a question I asked.
All sorts of things go to 0 and/or ∞ if you start boosting at c, and
so you cannot boost into and out of a photon's frame.
It ...
5
votes
0answers
65 views
Why is there no UV catastrophe (divergence) in turbulence?
I have just read that as the Reynolds number is increased, the separation of macroscopic and microscopic scales increases and that this also means that there is no UV catastrophy (or equivalently UV ...
1
vote
1answer
52 views
Defining the star as the ellipse focus rather than the barycenter, what does the other focus do? [duplicate]
There are a lot of images and animations on the internet depicting two bodies orbiting around their common barycenter. The barycenter is defined as the (let's say right) focus of the ellipse.
If we ...
4
votes
2answers
77 views
What would happen if energy was conserved but phase space volume wasn't? (and vice-versa)
I'm trying to understand the relationship between the two conservation laws. As I understand, Liouville's result is a weaker condition: it relies merely on the particular form assumed by Hamilton's ...
0
votes
0answers
45 views
What force does the seat exert on the rider at the top and bottom of the ride? [closed]
A 75 kg person rides a Ferris wheel which is rotating uniformly. The centripetal force acting on the person is 45 N. What force does the seat exert on the rider at the top and the bottom of the ride?
2
votes
0answers
37 views
What is three-photon interference?
Whilst reading this paper on a quantum processor that performs a type of matrix computation, I came across the concept of 'three-photon interference'. A quick Google search shows that this process is ...
0
votes
1answer
53 views
The second resonance of string?
What is the relationship between "the second resonance " and string and the wavelength. Like in this question: if the length of the string is 2cm with second resonance, then what is wavelength?
4
votes
1answer
64 views
Highest naturally occuring binding energy of electrons
I was wondering which element has the highest binding energy of an electron. Is it simply the 1s electron of the heaviest stable element? If so, can somebody tell me where I can find a table of ...
2
votes
3answers
83 views
Spherical inversion in terms of special conformal transformation
I want to consider conformal maps on suitable compactifications of $\mathbb{R}^{n}$. I know that a special conformal transformation: $$x_i\mapsto\frac{x_i-x^{2}b_i}{1-2b\cdot x+b^{2}x^{2}}$$ can be ...
0
votes
1answer
65 views
How is torque equal to moment of inertia times angular acceleration divided by g?
How is the following relation true
$$\tau = \large\frac{I}{g} \times \alpha$$
where $\tau$ is torque,
$I$ is moment of inertia,
$g= 9.8ms^{-2}$,
and $\alpha=$ angular acceleration.
4
votes
1answer
114 views
Stark Effect on the 1st excited state of Hydrogen
I know the ground state of hydrogen is unaffected by the Stark effect to first order. And I also know that the 1st excited state is split from 4 degenerate states to 2 distinct, and 1 degenerate state ...
0
votes
1answer
49 views
Zero uncertainty constant and a unit change
So, we know the speed of light with zero uncertainty. We also know that values of $\epsilon_0$ (electric constant) and $\mu_0$ (magnetic constant) are known with zero uncertainty.
My questions are ...
3
votes
1answer
84 views
A corollary of Mermin-Wagner Theorem
The picture above shows Mermin-Wagner Theorem and its corollary. How can the corollary be derived from Mermin-Wagner Theorem?
0
votes
0answers
44 views
Is this picture of the electron dipole moment correct?
It's the electron spinning on its axis, and a magnetic moment shoots up. The direction of the North-South is opposite what I thought it should be. Why is the vector arrow pointing from North to ...
4
votes
0answers
70 views
Mechanical Equivalent of Heat
Recently I have been looking up James Joule's experiment regarding the mechanical equivalent of heat. After viewing some drawings of the apparatus, I assumed that the lines holding the weights would ...
4
votes
1answer
43 views
What is the minimum pressure difference for your ears to pop?
I'm assuming the answer to this largely varies from person to person. Assuming you could instantly change the pressure around your head by amount $\Delta p$, what is the minimum $\Delta p$ for your ...
3
votes
2answers
108 views
Geodesic equations
I am having trouble understanding how the following statement (taken from some old notes) is true:
For a 2 dimensional space such that $$ds^2=\frac{1}{u^2}(-du^2+dv^2)$$
the timelike geodesics ...
-1
votes
2answers
82 views
Einsteins train though experiment. What if the train is moving at the speed of light? (layman Q) [closed]
I understand einstein's train paradox. Where one man on a platform is passed by a man in a traincar, at the moment they meet a flash of light is given off in the middle of the train car. To the man on ...
2
votes
0answers
48 views
Mass spectrum of Type I string theory
I understand that the massless fields of the Type I string theory are the described by:
[\begin{array}{*{20}{c}}
{{\rm{Sector}}}&{{\rm{Massless fields}}}\\
{{\rm{R - R}}}&{{C_0}}\\
{{\rm{NS - ...
1
vote
0answers
63 views
Fermi level for the bulk of topological insulator
"Fermi level" is the term used to describe the top of the collection of electron energy levels at absolute zero temperature. Why does the Fermi level for the bulk of topological insulator fall within ...
1
vote
1answer
39 views
Distribution of pressure inside a capsule
How would pressure of an ideal gas be distributed over the inside of a capsule (a cylinder with semi-spheres on the ends)? What about the strain on the material? Is there a general formula for how ...
0
votes
2answers
87 views
What if the antimatter in the center of our galaxy could annihilate and cause a chain reaction?
Being said that the antimatter - matter reaction is faster than that of a fission and fusion, what if the antimatter cloud found at the center of our galaxy could really able to react with matter from ...
2
votes
1answer
45 views
Thermodynamics, PV diagrams?
My teacher told me that the total amount of work done on or by a gas can be represented by the area enclosed in the process in a PV diagram. This is only valid for non isothermic processes, right?
2
votes
3answers
134 views
Why is the Coulomb potential in pseudo-2D experiments proportional to the logarithm of distance?
Inspired by this question, I ask another. Theoretically, Coulomb potential in 2D is proportional to the logarithm of distance; In experiments, though electrons are constrained in a pseudo-2D ...
5
votes
2answers
158 views
First law of thermodynamics?
The first law says that the change in internal energy is equal to the work done on the system (W) minus the work done by the system (Q). However, can $Q$ be any kind of work, such as mechanical work? ...
0
votes
1answer
42 views
Does the actual curvature of spacetime hold energy?
My understanding of GR is that curvature of spacetime reflects the density of energy-matter. Does the curvature itself have energy? Or if energy is assigned to curvature it simply reflects the energy ...
4
votes
1answer
110 views
Why do wind power plants have just 3 blades? [duplicate]
Why do wind power plants have just 3 blades? It seems that adding more blades would increase the area that interacts with the wind and gather more energy.
(Image from Wikipedia.)
1
vote
2answers
68 views
Is it possible to obtain higher order corrections to the ideal gas law when one allows realistic phenomena to make their way into the equations?
I had an interesting thought today that caused me to ask whether it'd be possible to make corrections to the ideal gas law via introducing terms derived from more realistic phenomena to make their ...
-3
votes
1answer
26 views
How to find time taken for a spinning top to stop? [closed]
The angular position of a spinning top is given by $\theta = t^3 - 72t$, where $t$ is in seconds
and $\theta$ in "radian".
3
votes
3answers
111 views
Physical interpretation of Poisson bracket properties
In classical Hamiltonian mechanics evolution of any observable (scalar function on a manifold in hand) is given as
$$\frac{dA}{dt} = [A,H]+\frac{\partial A}{\partial t}$$
So Poisson bracket is a ...
0
votes
2answers
57 views
Is there any correlation between mass-energy equivalence and Maxwell's 4th equation?
I wonder, how came in both equations proportionality constant is exactly $c^2$?
$$c^2(\nabla \times B) = \partial E/\partial t$$
where $E$ - electric field
$$c^2m = E$$
where $E$ - energy
I am ...
0
votes
1answer
45 views
Speed of Light and Information
Einstein in his thought experiment(?) for the constancy of speed of light in vacuum in all frames reasoned , that if speed of light of vacuum isn't constant than you'll be able to perceive effect ...
1
vote
2answers
161 views
Excluding big bang itself, does spacetime have a boundary?
My understanding of big bang cosmology and General Relativity is that both matter and spacetime emerged together (I'm not considering time zero where there was a singularity).
Does this mean that ...
0
votes
1answer
95 views
Neutrinos and Speed of light
Einstein's Special Theory of relativity postulates that the speed of light is same for all frames.
Suppose a neutrino is there moving at the speed of light. Then will that neutrino also be flowing ...
6
votes
1answer
131 views
Our Universe Can't be Looped? [duplicate]
With reference to the Twin-Paradox (I am new with this), now information of who has actually aged comes from the fact that one of the twins felt some acceleration. So if universe was like a loop, and ...
1
vote
2answers
35 views
MRI's and Electromagnetic Radiation
If the waves in an MRI can go through our body, why is it that light with its magnetic fields gets stopped at our skin?
3
votes
1answer
35 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 at ...
0
votes
1answer
34 views
Light-Particle Wave Duality
There is a lot of reading to do on this to fully understand it, but without doing that reading is there a short explanation as to why and how light behaves as a wave and a particle?
2
votes
1answer
87 views
Photons, where do they come from? [closed]
Photons, where do they come from?
What exactly is a photon?
I've certainly heard how they get produced, but it doesn't seem to make sense that some sort of particle should need to be produced just ...
3
votes
1answer
36 views
Parametrization of $U(N)$ non-linear sigma model
The motivation of this question actually comes from this (really old) paper of Weinberg. He considers a theory of massless pions. They have a chiral $SU(2)_{L} \times SU(2)_{R}$ symmetry. The pions ...
0
votes
2answers
83 views
The status of $SU(3)_C$ symmetry in the Standard Model
In the Standard Model of Particle physics the $SU(2)_{EW}$ symmetry and the $SU(2)$ isospin symmetry are broken. What about $SU(3)_C$? Is it broken too?
if YES, what breaks the symmetry?
If NO, what ...
0
votes
2answers
51 views
intensity of electromagnetic waves
I have a trouble understanding intensity of electromagnetic waves,
I already looked at this article and this question but didn't understand completely
$Intensity = \frac{\epsilon_0}{2} |\vec ...
-1
votes
2answers
48 views
If there were two equal masses with one mass in the middle which way would gravity pull it?
If there were two masses with a third exactly in the middle of those two, which way would the middle mass be pulled?
