Quantum Theory of Earth Satellite Analogy to Bohr Model

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Homework Help Overview

The discussion revolves around developing a quantum theory of Earth satellites, drawing an analogy to the Bohr model of the hydrogen atom. Participants are tasked with deriving expressions for the orbit radius and energy in terms of quantum numbers and relevant parameters, using a satellite of mass 1000 kg in a circular orbit of radius 7000 km as a case study.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of the Bohr model equations to the context of satellites, questioning the appropriateness of using the Rydberg constant and the implications of gravitational versus electromagnetic potential. Some suggest using the Sommerfeld-Wilson quantization condition for angular momentum as an alternative approach.

Discussion Status

The discussion is ongoing with various interpretations being explored. Some participants express uncertainty about the use of constants and the relationship between gravitational and electromagnetic systems. There is a recognition that the quantum number may be large due to the scale of the problem, and guidance has been offered regarding the limitations of the Rydberg constant in this context.

Contextual Notes

Participants note the challenge of adapting the Rydberg constant, which is specific to atomic systems, to a gravitational context. There is also mention of the need to consider the mass of the satellite and the implications of charge in the analogy.

Rapier
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Problem:
In analogy to the Bohr Theory of the hydrogen atom, develop a quantum theory of Earth satellites, obtaining expressions for the orbit radius (r) and the energy (E) in terms of the quantum number (n) and the other relevant parameters. A satellite of mass 1000 kg is in a circular orbit of radius 7000 km, to what value of n does this correspond?

Equations and Constants:
Bohr Model: E = -R*h/n^2
E = 1/2 * m * r^2 * ω*2
ω = v/r
v^2 = G*M/r
R = 1.0973 x 10^7 m^-1
h = 6.626x10^34 kg*m^2/s
M = 5.972x10^24 kg
G = 6.674x10^-11 m^3/(kg*s^2)

Attempt:
E = -R*h/n^2
1/2 * m * r^2 * ω*2 = -Rh/n^2
r^2 = -2*R*h/(n^2 * ω^2 * m)
r^2 = -2*R*h*r^3/(n^2 * G* M * m)
1/r = -2*R*h/(n^2 * G* M * m)
r = (n^2 * G* M * m) / (-2*R*h)

Just by parsing the units I know I've taken a wrong turn. I've tried multiple times and I appear to be missing a velocity term somewhere with the (-2*R*h). I think I'm missing something simple, I just don't see it.

Thanks.
 
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Rapier said:
E = -R*h/n^2
If R is the Rydberg constant: the potential of Earth is not the same as the one of an electron in an atom.

Edit: I moved the thread to the homework section.
 
Last edited:
It's probably simpler in this case to use the Sommerfeld-Wilson quantization condition on the angular momentum of the satellite. You will find that since ##h## is so small compared to the other scales of the problem that the quantum number is huge and different quantized orbits are so close together as to be beyond distinguishing within the precision of the measurements that we could make.
 
mfb said:
If R is the Rydberg constant: the potential of Earth is not the same as the one of an electron in an atom.

Edit: I moved the thread to the homework section.

I'm not sure what to use for R then because my definition of R includes the mass of an electron and the charge. I can see replacing the mass of an electron with the mass of my satellite, but then what do I do with the charge? I tried to analyse the units to come up with a value but I got nothing that made any sense.

Oh, and thanks for moving it! :)
 
fzero said:
It's probably simpler in this case to use the Sommerfeld-Wilson quantization condition on the angular momentum of the satellite. You will find that since ##h## is so small compared to the other scales of the problem that the quantum number is huge and different quantized orbits are so close together as to be beyond distinguishing within the precision of the measurements that we could make.

Oh, that does look more promising. Let me give it a stab.
 
Rapier said:
I'm not sure what to use for R then because my definition of R includes the mass of an electron and the charge. I can see replacing the mass of an electron with the mass of my satellite, but then what do I do with the charge? I tried to analyse the units to come up with a value but I got nothing that made any sense.

Oh, and thanks for moving it! :)
You cannot use the Rydberg constant - it is specific to the electromagnetism problem in an atom. You can see how it is derived based on the potential energy, however, and use this with the gravitational potential instead.
 

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