0
votes
0answers
2 views

Response curve shape transformations with different units photon energy and photon count

I have response efficiency curve (for an optical component) as a funtion of wavelength. The values are dimensionless numbers between 0 and 1. The curve I have now, say f1(lambda), refers to the ...
0
votes
0answers
2 views

Why does my hands' hairs get clinged to my cathode-ray TV?

My dad's old TV! When I switch it off after watching and get my hands closer, my hands' har get attached to the screen. And it sticks for sometimes! Now, I know how a cathode ray oscilloscope works. ...
0
votes
0answers
7 views

Why are Rainbows always seen Horizontally or from Sideways?

We see Rainbows many times, but we always see them Horizontally or from Sideways. Why can't we see it from under it?/From the point where it starts or ends(end points)?
0
votes
0answers
11 views

Wave Equation Variables and Interpretation

Consider the scalar wave function $\exp[i(kr -\omega t)]$, where $k$ is the wave number and $r$ is the spatial coordinate. We can alternately define $k$ to be a vector that gives the direction and ...
0
votes
0answers
8 views

Maximum velocity in a viscous fluid

Situation: A viscous fluid is flowing through a tube, and the rate of ejection is x $m^3s^{-1}$ Finding the velocity of the ejected fluid would be simple enough, by dividing the rate of ejection by ...
0
votes
1answer
22 views

How to know if a wave function is physically acceptable solution of a Schrödinger equation?

How does one decide whether a wave function is a physically acceptable solution of the Schrödinger equation? For example: $\tan x$ , $\sin x$, $1/x$, and so on.
0
votes
0answers
13 views

Symmetry Group of system to a given Hamiltonian

I want to determine the symmetry group of the following system: I consider a charged particle in a spherically symmetric potential $V$ and a homogeneous electric field of magnitude $E$ in ...
1
vote
0answers
6 views

How did Planck use the concept of statistical entropy in trying to understand the physical meaning of his own law?

I was reading Introducing Quantum Theory: A graphic guide (by J.P.McEvoy & Oscar Zarate) and came across Planck's predicament of understanding his very own law that accurately explained the ...
2
votes
0answers
23 views

Induced current created by a magnet falling in a copper tube?

One of the educational demos often shown in schools is to drop a high strength neodymium magnet down a length of copper tube. It takes a considerable time to exit the tube because as it falls it ...
4
votes
2answers
80 views

Why doesn't this multiplication of Grassmann variables give the expected result?

Would anyone be able to tell me how srednicki goes from step $(44.29)$ to $(44.30)$? Here is the paragraph: Now let us introduce the notion of complex Grassmann variables via $$\begin{align} ...
1
vote
0answers
16 views

Can a gravitational wave produce oscillating time dilation?

I was reading about gravitational waves and about laser based detectors. I also read this. As mentioned in the answer, when ever there is a deformation in spacetime, doesn't it also create a minute ...
0
votes
4answers
37 views

Is it true that water go down the drain counterclockwise in the northern hemisphere and clockwise in the southern [duplicate]

Many websites say that water drain in different directions in Northern, Southern hemispheres. Some people say that Coriolis effect causes it. Some people say that it's not true.
-3
votes
0answers
15 views

Why, Brush may start moving when placed on a vibrating horizontal surface? [on hold]

A brush may start moving when placed on a vibrating horizontal surface. Investigate the motion.
0
votes
3answers
31 views

How would filling a milk canister with helium affect the reading it makes on a scale?

Let's say that if I put a milk canister on a scale it shows 10kg. If I fill it with Helium it must necessarily be less than this, right? Can someone explain this (probably trivial) thing to me? :) ...
0
votes
0answers
11 views

Existence of a statistical biophysics study? (In Fitzhugh Nagumo diffusion system with non linear waves)

Is there any field of biophysics or any previous research done in the field Fitzhugh Nagumo reaction-diffusion equations to create nonlinear waves in biological tissues (such as muscle tissue) that ...
2
votes
2answers
89 views

What is the luminosity of the Milky Way galaxy?

The luminosity of the Milky Way galaxy according to this is $5\times10^{36}$ Watts, but this number suggests that there are about 10 billion stars with Solar luminosities in the Milky Way, which ...
1
vote
3answers
185 views

Do atomic orbitals exist in a fully ionised atom?

Say a H atom is ionised and then it captures a free electron at a later time, do the atomic orbitals then have to go through a transitory phase to accommodate the electron before they form the correct ...
1
vote
0answers
25 views

Is there always an equilibrium point in space for gravity?

For instance, for a two-body system, there will always be a point in-between the two in which the forces of gravity completely cancel, and if I were there then I would experience no net force. I ...
0
votes
0answers
16 views

Why do we assign an electric field vector to an EM wave when photons have zero charge? [duplicate]

In the standard model photons have no charge. So how can en EM wave be given a quantity of electric field to do work on electrons in say a RF antenna. What excites the electrons? I may have parts of ...
0
votes
2answers
28 views

What happens to an orbiting body moving with the Earth's angular speed at various altitudes?

I was learning about inertial frames amongst other things, and I somehow came up with this question. Imagine we have a pole, made of imaginary very strong material that will never bend, placed at the ...
2
votes
0answers
30 views

Can different guns make the same ammo more effective at penetration? [on hold]

I was watching an episode of Law & Order in which someone was shot with a TEC-9. The ballistics expert said "TEC-9...unsurpassed for penetrating steel doors". I have never even handled a real gun ...
-2
votes
0answers
16 views

Projectile motion with respect to integrating equation of motion [on hold]

Explain projectile motion with the help of "integrating equation of motion"
16
votes
1answer
876 views

Why are dishwasher washed glasses “squeaky clean”?

They seem to have increased friction after going through a dishwasher. The unpleasant (to me) squeaky feel is probably slip-stick friction exciting resonance in the glassware. But why? What has ...
1
vote
1answer
42 views

Why do derivatives act on vector fields on a worldsheet?

The covariant derivative of a vector $A^{\mu}$ at a point $x$ is defined as $$D_z A^{\mu}=\partial_zA^{\mu}+\Gamma^{\mu}_{\rho\sigma}(x)\partial_{z}x^{\rho}A^{\sigma}$$ where Greek symbols are ...
0
votes
0answers
28 views

Rotation systems. Problem interpreting an equation

In this equation: Why is $(\frac{d}{dt})_r \bf{\Omega} \times \bf{r}=\frac{d\bf{\Omega}}{dt}\times\bf{r}+\bf{\Omega}\times \bf{V_r}$ In particular, I have qualms with the term ...
0
votes
0answers
15 views

Why resistance should be increased for Photoresistor in night for Street Lamps? [migrated]

I can't get why the resistance for a Photoresistor should be increased at night time as said in Photoresistors. The reason is that I think that to turn on a light it's better not to have a higher ...
0
votes
0answers
9 views

Virtual geomagnetic pole [on hold]

Magnetic measurements have been made on some lavas found at 60ºN and 90ºW. The inclination angle is 37º. If the horizontal direction of magnetism of these lavas is due west, calculate the position of ...
0
votes
0answers
19 views

Probabilities with a qubit

A two-state quantum system has orthonormal energy eigenstates ψ1 and ψ2, with energy eigenvalues E1 and E2 = E1 + ∆E (∆E > 0). These energy eigenstates form a complete set of wavefunctions for the ...
1
vote
1answer
29 views

Why is cross section inversely proportional to wavelength for interstellar scattering?

The following problem was part of a homework for my Cosmology class: Compare the probability of interstellar scattering of photons of yellow light (5000 angstroms) and 50 micron infra-red light. ...
2
votes
3answers
47 views

Why do Signs Fall?

My question in this post is, why do signs with large angles fall? For example, fold a piece of paper in half, set the angle between the two halves, and place it on the floor; it will stand or collapse ...
2
votes
1answer
17 views

Formation of supermassive black holes

Scientists have found very bright source of light which they call quasar and the are found to be supermassive black holes. So these black holes are so massive that they cannot be formed by a ...
1
vote
1answer
69 views

Fourier and inverse fourier transform in QFT

According to my lecture notes, the inverse Fourier transform of an operator $\phi(p)$ is given by $$\phi(x)=\int \frac {d^4p}{(2\pi)^4}\phi(p)e^{-ip\cdot x}.$$ As @WenChern pointed out below, Peskin ...
1
vote
0answers
29 views

Lorentz transformations on momentum space Weyl spinors

The Weyl spinor in momentum space can be given by the inverse Fourier transform: $$\psi_L(x) = \int \frac {d^4 p} {(2\pi)^4}\psi_L(p)e^{-ip\cdot x}.$$ In addition, Lorentz transformations act on ...
2
votes
1answer
39 views

How can the Andromeda Galaxy alone have more mass than the Local Group?

I was reading about the Local Group, and it is stated that the total mass of the group is $1.29±0.14 × 10^{12}$ Solar masses. The number actually felt a bit low to me because I know the Milky Way ...
0
votes
1answer
19 views

Difference between solid and gases thermal expansion

The coefficient of linear expansion is $$\Delta L = L \,\alpha \Delta T,$$ where $\Delta t$ can be the difference of any two temperatures. However, in volume expansion of gases, $$\Delta V = V ...
0
votes
0answers
16 views

How to model drag coefficient during initial acceleration

Using a $0.4\text{ m}$ cubic parachute (cruciform design with holes in the corners for stability), a drag coefficient of about $1$ is expected for Reynolds numbers about $10^4$ (velocities about $1 ...
1
vote
1answer
33 views

How to account for inertia in kinematics?

Alright, I'm only in AP Physics and I asked my teacher and he couldn't help me... I'm making a 2D physics engine and I'm having problems when it comes to gravity between objects and I think its ...
0
votes
1answer
13 views

Water behaviour under theoretical near-infinite pressure conditions

I've asked a similar question here but the answer given shows the behaviour of water under general conditions. I'd like to know what the behaviour of water is like as pressures increase towards ...
2
votes
1answer
17 views

Question about wavelength of EM wave in dielectric

Many websites (http://maxwells-equations.com/materials/permittivity.php) lists out the following formula as to how you can compute the wavelength of an EM wave in a dielectric $$\lambda_d = ...
1
vote
0answers
38 views

How do Lorentz transformations act on position kets $|\mathbf{x}\rangle$?

The Hilbert space of one particle can be spanned by position kets $|\mathbf{x}\rangle$ or by momentum kets $|\mathbf{k}\rangle$. If we denote $|k^\mu\rangle = \sqrt{2E_{\mathbf k}}|\mathbf{k}\rangle$, ...
0
votes
1answer
23 views

How does one figure out how fast water is moving through a water intake on a dam?

Say the dam is Hoover dam for example. The intake is where the water flows in to turn the turbines that generate electricity. I want to know if there is an equation that describes the speed of the ...
0
votes
0answers
9 views

Non-minimal coupling (Pauli Coupling) of gauge field with a non-relativistic scalar field

I am wondering if it makes any sense to non-minimally (say, Pauli-like) couple an external gauge field with a non-relativistic scalar field: \begin{equation} p_\mu \rightarrow p_\mu - e A_\mu + ...
0
votes
1answer
31 views

Finding Lagrangian with Non-holonomic constraints

I am stuck working on a problem that involves finding the Lagrangian for a free particle constrained to move on the surface of a disk of radius $a$. The particle collides elastically with the edge of ...
0
votes
3answers
50 views

EPR Paradox resolution: the spin is fixed at creation but its measurement isn't?

The Wikipedia article on the EPR paradox uses the example of an electron and positron created from a common source, each moving in an opposite direction to the other. Detector A is used to measure the ...
3
votes
1answer
42 views

Can unpolarized light be created from polarized light?

I have a question regarding this topic. According Stokes Parameters theory, unpolarized light could be described as a superposition of two independent beams of equal intensity and orthogonal ...
0
votes
0answers
22 views

Combining Moment of Inertia Tensors

In a physics simulation of rigid bodies, if I have a cube with a known mass and moment of inertia tensor, and I attach it to another cube with a known mass and moment of inertia tensor such that its ...
0
votes
0answers
19 views

Examples of systems with linear response behavior

I've checking the linear response theory and there are 3 fundamental assumptions. 1) Linearity of the response of the system to an external excitation, 2) Stationary response function: ...
0
votes
2answers
42 views

What unit would the answer be in?

So I have used this formula: $$W= PV_1 \times \ln\frac{V_2}{V_1}$$ and I have converted my values to cubic meters and pascals. So Work Done, $W$, what would be the unit for that answer? I already ...
0
votes
3answers
36 views

Conceptualization and modelling of spin

I'm trying to get a decent understanding of the bell inequality, and so am trying to understand spin both conceptually and mathematically. When I picture spin, I imagine a sphere rotating about its ...
0
votes
0answers
27 views

Maxwell's Equations for Accelerated Conductors

I asked a question about accelerated conductors in a magnetic field but nobody unfortunately answered. That is: Ohm's Law for Accelerated Conductors Maybe, I could not state my question well. I ...

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