0
votes
2answers
107 views

Can a hydrogen atom sit still?

Can we take a single lone hydrogen atom (proton and electron?) and set it in one place and observe it staying there? How about just a proton? A neutron? How about just an electron?
0
votes
2answers
148 views

Deriving spring oscilation period [duplicate]

We have a spring attached to a wall and at the other part an object on a frictionless surface. I tried to calculate the spring oscilation period. I used the conservation of energy and kinematics ...
0
votes
1answer
28 views

Effect of crystal growth on its scintillation

How does crystal growth affect its scintillation properties? What are possible ways in which growth of CaWO crystals grown via Chochralski method could be modified to avoid non-linearity in its ...
9
votes
3answers
563 views

Historical analysis of light interference - difference frequencies

It is well-known that light of two different frequencies illuminating a detector will produce an output with a component at the difference frequency. While such considerations are eminently useful (...
0
votes
1answer
109 views

Which function denotes the energy of thermal motion within a system?

In thermodynamics, the heat $Q$ is defined as a type of energy in transfer, and is not a state function, which function denotes the energy of thermal motion within a system? 1) $TS$, (there is a ...
4
votes
1answer
280 views

Berry's phase: in which space does the degeneracy appear?

This question follows a previous one of mine: Adiabatic theorem and Berry phase. In his original paper [ M. V. Berry, Proc. R. Soc. Lond. A. Math. Phys. Sci. 392, 45 (1984) ], Berry discussed the ...
7
votes
3answers
203 views

In a radioactive Bose-Einstein condensate, would all the atoms disintegrate simultaneously?

They're all supposed to do the same thing - so I suppose they would? Also, would the resulting half-life be the same as that of the individual atoms it is made up of?
2
votes
2answers
2k views

How to calculate the drag coefficient using terminal velocity?

I was wondering if it were possible to calculate the drag coefficient by allowing an object to reach terminal velocity. Can you rearrange the terminal velocity formula to give the drag coefficient?
2
votes
1answer
2k views

Kinetic energy and potential energy variation over distance in SHM

When you compute the average potential energy of a horizontal spring mass system from the mean position to the positive amplitude A, the value comes out to be $\frac{1}{6}kA^2$. For the average ...
1
vote
0answers
31 views

What is it that makes an electron maintain a distance from the positively charged nucleus? [duplicate]

What is it that makes an electron maintain a distance from the positively charged nucleus? Why aren't electrons merely pulled into and absorbed by the nucleus ?
2
votes
3answers
742 views

Describing a circular current loop as delta functions

It would be really nice to see how Jackson got eqn 5.33 on his example problem for finding the vector potential of a circular current loop $$ J_{\phi}=I\sin\theta'\delta(\cos\theta')\frac{\delta(r'-a)...
4
votes
3answers
330 views

In scattering, how does a particle 'know' which direction it is being illuminated from?

In scattering experiments, for example light scattering, the scattering strength from different sized particles is depicted as below. What I can't understand is: how does a particle know which ...
1
vote
1answer
91 views

Distance and velocity question

I know that speed is the derivative of distance. So integrating speed should give you distance. Let's suppose we have a speed which obeys this function: $$ v(x) = 2^{2^x} $$ So at time 0 the speed ...
2
votes
2answers
200 views

How “unnatural” is the universe? [closed]

Looking to read up on the impact the discovery of Higgs boson has on the String Theory I came upon these two paragraphs in an article about the Higgs boson Nobel Prize: One possibility has been ...
22
votes
4answers
5k views

How did they take photos of Jupiter?

How did they take photos of Jupiter - I mean Jupiter is illuminated and that's a lot of light to produce. Am I missing something, and there was some sort of dark photo technology used, or was there ...
3
votes
2answers
330 views

Cartesian Coordinates to Polar Coordinates

I apologize if this question is trivial, but I am new to physics and am struggling with some of the basic concepts. Working in $\mathbb{R}^2$ with standard coordinates $(x,y)$, suppose we have a ...
3
votes
1answer
175 views

Killing Equation, trouble with tensor algebra

I'm attempting to follow a proof that the commutator of two Killing vectors is itself a Killing vector. The source that I've posted is from my course notes. I've highlighted the part I'm stuck on. ...
1
vote
1answer
259 views

Woodwind instruments overtones [duplicate]

When playing woodwind instruments, e.g., flute, if one blows harder, the sound will be one octave higher. Even harder gives even higher overtones. Does anyone know why?
2
votes
1answer
66 views

Where will a board break when weight is added to the end?

If you have a board, say a standard 2x4 of finite length, where one end is fixed in a cement wall and the other end is free, and you begin adding weight to the free end until it breaks, where will the ...
4
votes
1answer
386 views

Variation in measurements of $g$ on the Earth's surface due to the Moon's gravity

A book, Exercises for the Feynman Lectures on Physics, has recently been published. It consists of homework problems to provide practice with the techniques and concepts used in the famous Feynman ...
2
votes
3answers
705 views

Intuitive explaination for why higher engine compression ratio is more efficient?

Intuitively to me it seems likes increasing compression ratio would require more work to compress the gasses before ignition, so you'd just end up getting back what you put in - like a spring. What am ...
1
vote
4answers
493 views

Double rainbows

In my garden, when I'm watering the plants I sometimes see a rainbow or two. How did two rainbows appear? Why can't I see three rainbows then, or how can I see three rainbows?
1
vote
2answers
324 views

The Alcubierre drive and closed timelike curves

Under what conditions would it be possible to create closed timelike curves, assuming an Alcubierre drive could exist? Would it be possible to have the latter without the former? See here for ...
0
votes
2answers
614 views

How to show that the gravitational potential energy of a two particle system is -2 times the total kinetic energy, without using the virial theorem?

Consider a two-particle system with identical masses, orbiting in circles about their center of mass. I'm supposed to prove that: $$U_p = -2U_k$$ With $U_p$ potential energy of the system, and $U_k$ ...
0
votes
3answers
332 views

Is duplication of nucleus, electron and proton (sub-atomic particles) possible? [closed]

usually a single cell develops into a huge mass to form a substance or an organism. is this happening because of multiplication of sub-atomic particles? if yes, then is it possible to multiply the ...
3
votes
0answers
213 views

Free charge movement in an electric field - including bremsstrahlung

Let us imagine a free, negatively charged object that is in rest and placed in an elecric field of a point positive charge. The positive charge has a huge mass and cannot move, so we consider only the ...
2
votes
1answer
373 views

Higher-Dimensional Metrics in (Hyper)-Spherical Coordinates

I want to compute the components of the Riemann curvature tensor (for a case similar to the Schwarzschild solution) in 4 + 1 dimensions, but I want to use a higher-dimensional analogue of spherical ...
2
votes
1answer
765 views

Fringe Pattern Brightness for Young's Double-slit experiment

Perhaps I have missed something in my notes, but I have noticed when looking at different sources that some textbooks/sites state that the fringe brightness for the young's experiment is the same for ...
2
votes
2answers
96 views

What is the performance of a silicon crystal that makes it an essential component to computing

I'm on a thread of interest in the precise physics that allow the creation of the computing process. It began as a question posted in search of an understandable explanation of what physical form ...
0
votes
1answer
329 views

How does an accelerating charge radiate electromagnetic waves? [duplicate]

When a charged particle gets accelerated it emits electromagnetic waves. In reality, when a charged particle gets accelerated the electric field around the charge remains unchanged, but the magnetic ...
3
votes
1answer
89 views

Can the rate of virtual pair production from vacuum be computed?

Consider for instance the QED Lagrangian. Is it possible to compute the rate of virtual electron-positron creation from the vacuum?
17
votes
2answers
2k views

Why is there no Gravitational Magnetic Field?

We think that the electric field and gravitational field operate similarly with their corresponding charges/masses. With just a difference that the electric field is sometimes attractive and sometimes ...
0
votes
2answers
89 views

Charge Distribution in Reissner-Nordström Black Holes

In an electrically charged black hole, such as the one described by the Reissner-Nordström metric (i.e. with no angular momentum), where would the electric charge be situated (neglecting any charged ...
0
votes
1answer
73 views

Quantum mechanical proof of Conway's SPIN and TWIN axioms?

I think I understand correlations of EPR-state and GHZ-state which deal with spin-1/2 particles and (-1, 1) measured values. Conway's state is spin-1 particle state with (-1, 0, 1) measured values. ...
3
votes
2answers
4k views

Why do my ice cubes stick together? [duplicate]

When I put ice cubes in a glass of water, I find that sometimes they will stick together and form a sort of "bridge" between them as they melt. There is usually a visible line where one ends and the ...
0
votes
2answers
380 views

Find electric field given the magnetic field [duplicate]

Given the magnetic field as a vector, how do I find the electric field?
3
votes
5answers
1k views

Why aren't units with powers, like cm³, surrounded by parentheses?

Since $\renewcommand{\unit}[1]{\,\mathrm{#1}} 1\unit{dm} = 10^{-1}\unit{m}$, it follows that $1\unit{dm^3} = 10^{-1} \times 10^{-1} \times 10^{-1} \unit{m^3} = 10^{-3} \unit{m^3}$. However, in ...
8
votes
2answers
2k views

How much more efficient is a road bike than a mountain bike? [closed]

What would be a good estimate on the difference of efficiency between a road bike and a mountain bike? A number of links cite all the usual reasons: thinner tires, better aerodynamics... But I'm ...
2
votes
0answers
35 views

Quantum Efficiency Estimation

Might there be a way to do a rough estimate of the quantum efficiency of a photo-detector like a CCD or CMOS sensor based only on a picture taken with it? I've read papers and guides (like this one: ...
1
vote
1answer
509 views

The commutator of Killing vectors

I'm going over an assignment for my general relativity course. My solution to the question below strikes me as too short, considering that it appeared in the "longer questions" section of the ...
1
vote
1answer
160 views

Kinetic energy operator in Dirac's relativistic quantum theory

In non-relativistic quantum theory $\hat{K}=\hat{p}^2/2m$, What is the Kinetic energy operator in Dirac's relativistic quantum theory?
1
vote
0answers
89 views

Why does inelastic X-ray scattering probe the longitudinal dielectric function as opposed to the transverse dielectric function?

Light is a transverse wave. Therefore, light in the optical range (i.e. visible light) couples to transverse collective excitations of a material when measuring the optical conductivity for instance. ...
2
votes
2answers
399 views

What is the difference between 'flow' and 'move'?

I just met with a very basic question.(Might even sound silly!) My textbook kinda says(not exactly), 'Whatever flows is a fluid'. That got me wondering because we are creating a whole category of ...
1
vote
1answer
3k views

Formula for Electrical Arc Length

I was playing with some High-Voltage the other day, when a question popped into my head. Can you calculate length of an electrical arc? It probably would be proportional to :- 1. Voltage of the source ...
2
votes
2answers
178 views

Polarizing beam splitters for X-rays?

What is the lower bound for the wavelength concerning polarizing beam splitters? Especially I ask for interferometer experiments with single photons. Of course I know that they exist for all ...
2
votes
2answers
89 views

In a Big Crunch, would there be more mass than at the Big Bang?

I found multiple questions where it is stated that dark energy increases as the universe expands. Assuming a big crunch scenario, will this dark energy "go away" again as the size of the universe ...
1
vote
2answers
213 views

Where does wave frequency come from

I am trying to wrap my head around where do oscillations in electromagnetic waves come from. As an example if I would take a string of guitar and ring it, it would produce a certain sound based on the ...
6
votes
3answers
770 views

How was the definition and the formula of work derived? Is it the best possible?

Work done is defined as the dot product of force and displacement. However, intuitively, should it not be the product of force and the time for which the body is acted upon by the force (force * ...
3
votes
1answer
148 views

Local number operators in quantum field theory

Redhead claims in his paper "More ado about nothing" (http://link.springer.com/article/10.1007%2FBF02054660) that number operators associated with different space points (at fixed time) fail to ...
2
votes
1answer
87 views

Forced vibration

Let's consider a spring which is subjected to forced vibrations: $$ F = F_0 \cos(\omega t) $$ Is the resonance frequancy $\omega_0$ of the spring dependent on the amplitude $F_0$? I ask this ...

15 30 50 per page