All Questions

I'm currently reading a book on optics, and have encountered a curious section: $$\nu = \nu'\sqrt{1-\frac{u^2}{c^2}} = \nu'\left(1-\frac{u^2}{2c^2}+\ldots\right)$$ This is the formula for the ...

Is there a cosmological model where the observable universe continues to shrink as time decreases, and continues to expand as time increases, and such that at both directions it never reaches the ...

the wave function of a particle sci =1/√2×{phoi0+phoi1} is given by in terms of eigen state phoi0 and phoi1 corresponding to the ground state energy and first excited state energy E0 and E1 ...

Is there a repulsive force between these two particles to prevent them from being in the same point? I mean, in order to obey Pauli exclusion principle?

A butyl rubber bag of total volume 3.0 m3 is used as a biogas digester. Each day it is fed an input of 0.20 m3 of slurry, of which 4.0 kg is volatile solids, and a corresponding volume of digested ...

Generally we read or solve problems about charges in the same medium. I wonder what would happen if the two charges were placed in different mediums. eg.) One is placed in vaccum and other is placed ...

The Robertson-Schrodinger or the generalized Uncertainty relation is given by $$\sigma_A^2\sigma_B^2 \geq \left| \frac{1}{2}\langle\{\hat{A}, \hat{B}\}\rangle - \langle \hat{A} \rangle\langle \hat{B}\...

I am reading this parer Majorana Corner Modes in a High-Temperature Platform,its model Hamiltonian is $H(\vec{k})=M(\vec{k})\sigma_z\tau_z+A_xsin(k_x)\sigma_xs_z+A_ysin(k_y)\sigma_y\tau_z+\Delta(\vec{...

Let us consider a two level system with eigenenergies $E_0$ and $E_1$ and corresponding normalized eigenfunctions $\psi_0$ and $\psi_1$. All the functions periodically depend on a parameter $\lambda$. ...

Is there any possible method to calculate electron positron projected range if we know CSDA and total stopping power . Can we just simple divide CSDA with density to get projected range . Also what is ...

What happens to the intensity of an electromagnetic wave if the amplitude of the electric field is halved?

n+ contact of p type Ge is ~700µm thick compared to p+ contact of n type Ge only ~0.3µm. The process of adding the contact is different. n+ contact Li is added by diffusion process but p+ contact B is ...

https://youtu.be/M07I1ompX54 Why does the spectral line change direction at minimum deviation position even if the prism table is rotated in the same direction?

If a cylinder is partially filled with granules and is rolling down an inclined plane, is there any relationship between the rotational motion of the granules and the motion of the cylinder? I'm ...

Radiation pressure at perfectly reflecting surface = 2I/c Radiation pressure at perfectly absorbing surface = I/c What will be the radiation pressure at a perfectly refracting surface? Will it be ...

$\renewcommand{\ket}[1]{\left \lvert #1 \right \rangle}$ $\renewcommand{\bra}[1]{\left \langle #1 \right \rvert}$ I'm wondering if we can recover the state of a composite system from the information ...

I am new to dark matter and modified gravity so excuse and inform me if I am wrong. If changes are made in the Friedman equations then there wouldn't always be an underlying action action principle. ...

Hubble’s law states that the recessional velocity is proportional to the distance. The further the observed distance, the further back in time one is observing. I want to know (generally) how this ...

Just curious. I’m kinda stumped and am interested in how one would go about visualizing/calculating this.

Is there any (simple!) explanation as to which of the following pieces of paper tape, each with the same number of holes, contains information: A simple coding of a Shakespeare sonnet The same ...

Why is it necessary to keep UTC within 0.9 seconds from UT1? I thought that UTC in fact more accurate than UT1, so why should it be based on UT1 within that range? Another question would be, why isn'...

We know that moving charge in constant velocity has deformed equation of electric field. $$ E = k \frac{1-\left(\frac{v}{c}\right)^2}{\left[1-\frac{v^2 \sin^2\theta}{c^2}\right]^{3/2}} \frac{q}{R^2}$...

I was reading an article in the newspaper today that referred to LIGO (and gravity-wave measurements in general) as "a new type of telescope". That got me thinking -- as I understand it, LIGO uses ...

For the flat geometry of lamda CDM model, the solution for Friedmann equation is $$ a(t) = \left\{ \frac{Ω_{m,0}}{Ω_{Λ,0}} \sinh^2 \left[\frac{3}{2} \sqrt{Ω_{Λ,0}} H_0(t - t_0)\right] \right\}^{1/3},...

My lecturer and I have found separately valid solutions to Poisson's equation in the region of interest for the following problem: Here is my interpretation of the boundary conditions: $$V(x,y,z \to ...

In staged rockets, each stage is jettisoned back to Earth after it completes its burn. Derive an expression for the total ΔV that a rocket can provide as a function of the number of stages, given a ...

I haven't had any physics class or anything close to that in a long time, and I'm currently confronted with an exercise I don't remember the formula(s) to solve it. Assuming I have an object of ...

Is it acceleration or speed that leads to time dilation or both? For example, when a spaceship accelerated to (almost) the speed of light, then reversed course to come back towards earth, does this ...

Naturalness has been a guiding philosophy for particle physics for a long time, but a few years ago I heard a talk by Nima Arkani-Hamed where he pointed out that it seems to have failed us as it ...

This is quite an interesting problem in astrophysics so I thought it would be a good idea to ask here so we can archive the solution for future reference. Consider a pulsar that emits pulses of ...

Calculate the wavelength of the xray emitted from a molybdenum target (z=42) when an electron moves from the L shell(n=2) to the K shell(n=1)

I am not much aware of Brownian motion and/or the Wiener process. Recently I have been reading a research paper where they mention a variable $dW$ as a "unit strength Wiener process". My question is ...

I downloaded the IntCal13, IntCal09, and IntCal04 datasets (parent site), and when I plotted the last 24k years was surprised to see a plateau or even reversal appear every ~5300 years. Apparently we ...

In quasi-classical approach the tunnelling probability through a barrier is given by the formula $$\text{prob}\sim e^{-\int p(x)dx}.$$ I left out the coefficients, with $p(x)\sim \sqrt{E-V(x)}$ being ...

I read about factorization in this two cases. First, since spin is not coupled with position and time it is possible to factorize the state in a spinor and a wave function. Second, in the 2 particles ...

Poisson's equation is $$\boldsymbol{\nabla}^{2}\varphi=-4\pi k_{e}\,\rho, \tag{*}$$ that in the case of a point charge $q$, already with spherical symmetry, has as solution \begin{equation} \varphi(...

I would like a rigorous explanation: a theory and model which describes glass as well as iron, and see why one of them is transparent; a detailed mathematical computation or a detailed reference. And,...

I am currently studying a eddy current disk break and came across this promising paper (PDF, princeton.edu) from 1942. However, in the first formula a suspicious $4\pi$ appears before the current $U(...

I'm given the following problem: "Consider an atom with orbital angular momentum $l$. What are the possible values of the total angular momentum quantum number $j$? Treat the case of $\ell = 0$ ...

The electric power dissipated due to a resistance is $P=RI^2$. What is the power due to a conductance?

about vertical axes passing through their centres, (as shown in figure) .a person of mass m sitting on circumference of disc a jumps with tangential relative velocity u w.r.t one rotating disc A jumps ...

Starting from the transformations of Lorentz, $$ \left\{\begin{aligned} x&=\gamma (x'+\beta ct)\\ y&=y'\\ z&=z\\ ct&=\gamma (ct'+\beta x')\\ \end{aligned}\right. \quad \tag{*}$$ I ...

I'm currently taking an introductory quantum mechanics course, where the last covered topic was spin and identical particles. During some reading online, I stumbled across the term "rotating a quantum ...

If so, what could be the impact of these reflections on the sun during an ice age on Earth?

Related to a previous post: Is there a Geometric Algebra for gravity? : I asked the question of whether gravity could be given a geometric interpretation though stated algebra. Because I first tackled ...

Let $K^\mu = V(x)U^\mu$ be vector proportional to the four-velocity $U^\mu$. (e.g. $K^\mu$ is a normalized time-like Killing vector for an observer at infinity). Then, $V(x) = \sqrt{-K_\nu K^\nu}$ is ...

In the discussion of the question "Nuclear Fusion with extremely high pressure and low temperature", the conclusion is only ultrahigh pressure cannot trigger fusion. But why does NIF try to use 192 ...

Is there a simple intuitive way to explain why energy-momentum density requires a tensor, while charge-current density is a vector? $\partial_{\mu} J^{\mu} = 0$ is a statement, in effect, that the ...

How could micro-states have uniform distribution in a 3D space unless there was 0 Gravity? Gravity violates the assumption of equal probability as it makes matter move in a predictable direction. ...

Does anyone have a clear explanation of how photoluminescence works? I know some of the basics, for example, that electrons are excited by photons to create excitons and when the excitons recombine, ...