# All Questions

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### Is there any defect in Rutherford's atomic model according to quantum theory?

According to quantum mechanics charged bodies do not emit energy continuously . Then why the atomic model of Rutherford has the defects of collapsing nucleus, continues spectrum.
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### Centripetal force and circular motion

When a body moves in a circular loop, there are basically two types of acceleration acting on the object. One is the linear acceleration which is basically tangent to the circle, and there is an ...
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### Quantised Angular Momentum?

So when learning about the Bohr model of hydrogen and de Broglie waves, it was shown that treating the electron of hydrogen as a de Broglie wave results in the relationship $$L=n\hbar$$ However, when ...
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### Quantum mechanics, operator commutes with Hamiltonian

My textbook said, if an operator $\hat{O}$ commutes with the Hamiltonian, then we can use the eigen vectors of the Hamiltonian as a basis of the Hilbert space, then express the operator $\hat{O}$ in ...
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### Why is radiance a measure for how bright an object appears if it is constant regarding the distance to the light source?

Radiance is flux per solid angle per unit area normal to the beam. Let’s say, you look at a piece of paper that is lit by the sun. Now you move twice as far away, the flux is then reduced by four due ...
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### Quantization conditions/ Real Scalar field

It is often written in books, the quantization conditions for classical field theory leading to Lagrangian of a real scalar field and thus to Klein Gordon equation. And these are introduced by ...
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### Can we calculate L-S coupling without Dirac equation?

It is known that there exists an orbital and spin angular momentum coupling for an electron moving in the atom. And the Hamiltonian can be directly derived using Dirac equation. I want to use a ...
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### Can a relativistic quantum particle be completely confined into a finite hole?

If we write the Klein-Gordon equation in this form \begin{equation*} c^2 \hbar^2 \nabla^2 \Psi = \hbar^2 \ddot{\Psi} + 2i\hbar (U - mc^2) \dot{\Psi} + U (2mc^2 - U) \Psi \end{equation*} we have a ...
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### How to prevent water droplets becoming larger on the tip of a nozzle?

I use an ordinary syringe to generate a single water droplet. However, it is not usually able to make a droplet smaller than 1 mm (because of surface tension forces, inner diameter of needle, etc.) ...
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### Does the medium matter when calculating Optical Period?

If I consider the optical period $T$ for a given wavelength $\lambda$ in vacuum, I can calculate it as: $$T = \frac{1}{f} = \frac{\lambda}{c}$$ However, in a particular material/medium, I am not ...
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### Force-carrying particles instead of forces

Are there physical theories in which notions of particle are used without the concept of force? I know about gauge bosons, see: http://en.wikipedia.org/wiki/Force_carrier and ...
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### What determines the magnitude of force of an electromagnet?

Let's assume that there is an electromagnet with $B = 1 Tesla$ , what is the magnitude of the force it could generate on other dipoles equal to it's surface area? Can the magnitude of force (in ...
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### Get angle to hit (x,y) with vertex [on hold]

In a projectile trajectory, I'm using the following equation to get the angle required to hit a target in x,y coordinates: This works great, however, it implies that the target is reached by one of ...
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### Why is UV index so high when storms are announced?

Everytime I check the weather news and storms are announced, the UV index is very often (if not always) "very high" or "extreme", why is that?
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### Mathematical Definition of Locality

What is the mathematically precise definition of principle of locality in physics for a continuous space-time in the sense that an object is only directly influenced by its immediate surroundings?
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### Is a model of helium atom without electron-electron repulsion solvable analytically?

Consider the following Hamiltonian: \hat H=-\frac{\hbar^2}{m_n}\nabla_n^2-\frac{\hbar^2}{m_e}\nabla_{e1}^2-\frac{\hbar^2}{m_e}\nabla_{e2}^2-\frac Q{|\vec r_{e1}-\vec r_n|}-\frac Q{|\vec r_{e2}-\vec ...
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### Optics simulation software for iypt #12 question thick lens

(As I'm writing these I viewed previous posts about optics simulation) me and some of my friends are working in iypt problems. one of the problem is named "thick lens" which says: A bottle filled ...
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### Why do we use time-dependent regions in this derivation?

I'm studying fluid mechanics and I have the following doubt: on the book, the author first deduces the differential form of the equation of balance of momentum. First he argues that if the fluid is ...
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### Do the strong magnetic field affects the Human Brain? if yes, then how? [on hold]

How this phenomenon occurs tell in detail
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### Flow in the strip $0 < x < \pi/2$, $y > 0$ [on hold]

Could anyone please explain how to show that a complex valued function represents a flow? For example, how does one show that $\Phi(z) = \sec^2 z$, where $z = x + iy$ with $x, y \in \mathbb{R}$, ...
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### Parallel Resistors (special cases formula)

1) A car's rear window defroster uses $n=15$ strips of resistive wire in a parallel arrangement. If the total resistance is 1.4 ohms, what is the resistance of one wire? Solution: I rearranged ...