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• Users: mjda
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1. ### How to use the Bremsstrahlung flux to analyse a medium?

I don't know where to even begin?
2. ### I The Confinement Radius of a Cosmic Ray (Galactic vs. Extra-galactic)

If we want to show whether or not a specific Cosmic Ray particle is confined to our galaxy we must use the Larmor radius (relativistic version), r = γmc / qB Considering a 10^14 eV proton and assuming the galactic magnetic field strength is 10^−11 T, show that the particle is confined to the...
3. ### I Ehrenfest Theorem: Enunciate & Implications for Classical/Quantum Mechanics

This may seem rather silly, but how would I go about enunciating Ehrenfest’s theorem? Also, does anyone know what this theorem implies for the relation between classical and quantum mechanics? Any suggestions or help is greatly appreciated!
4. ### I Energy Transport in Stars

I'm trying to understand why convection is an efficient mode of energy transport in the outer layers of the solar interior. Could anyone give me a little bit of knowledge? Thank you!
5. ### I The relativistic de Broglie equation

I am trying to find it in the form of: cP = hN where P and N are both the 4-Momentum, and 4-Wave vectors. It can also be written in the form: cm( u , ic ) = hf( cn / w , 1 ) c - speed of light m - mass u - 3-D velocity vector i - imaginary component f - frequency h - Planck's const. w -...
6. ### I Stellar Thermal Energy with no Nuclear source

Can anyone enlighten me as to why the total thermal energy of a star will increase with time if the star has no nuclear energy source?
7. ### I How to describe the Sun's interior?

Say one knows the mean density inside the Sun, and the mean temperature too, how can you use these to quantitatively justify reasoning?
8. ### I How to describe the Sun's interior?

My question to you is this... Can the interior of the Sun be described as an ideal gas? From my knowledge, to describe a body of gas as an ideal gas, the separation between the particles must be much greater than the size of the actual particles. How could one justify whether the Sun fits this?
9. ### Resolving bodies at large distances

Right?! I had it in my head that what if it actually means, how far can a body of similar size to the Sun be resolved at these wavelengths by the 6.5m telescope. My problem is "the stellar densities", and Solar neighbour hood, wording. If I have the angular resolutions at the respective...
10. ### I The relativistic de Broglie equation

It is in a question from a past paper I found. Maybe my wording is a bit misleading, but the exact phrasing is: By considering the scalar product of P both with itself, and with N, deduce the deBroglie equation.
11. ### I Covariance and invariance

Can anyone briefly explain the difference between covariance and invariance in terms of special relativity? My understanding is that an invariant quantity is a value which does not change regardless of frame of reference it is being measured in. Covariance is a value which when measured in...
12. ### I The relativistic de Broglie equation

I'm having trouble understanding how the 4-wave vector is derived, and also how it is then used alongside the 4-momentum vector to formulate the relativistic de Broglie equation. The inner product of the 4-momentum vector with itself, is an invariant quantity. If we define the 4-momentum...
13. ### Resolving bodies at large distances

Homework Statement If a 6.5m diameter telescope operates at wavelengths between 600nm to 2800nm, and for stellar densities similar to the Solar neighbourhood, what is the range of distances this telescope can resolve individual stars? Homework Equations The Attempt at a Solution My attempts...