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bio website sjbyrnes.com
location Massachusetts
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visits member for 3 years, 1 month
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19h
answered “Lack of inversion symmetry” in crystal?
1d
revised Justification of discrete spectrum for V(x) unbounded at $\pm \infty$ in Pauling and Wilson
added 68 characters in body
Jul
18
comment Total internal reflection and waveguides
Could you clarify, either (1) You want to learn how to derive the Fresnel equations, or (2) You want to know how you can calculate the angle-dependent phase shift starting from the Fresnel equations, or (3) Both.
Jul
14
answered Justification of discrete spectrum for V(x) unbounded at $\pm \infty$ in Pauling and Wilson
Jul
14
comment How can molecule of a few angstroms absorb visible light of a few hundred nanometers?
If you want to understand the cross-section or linewidth of an atomic absorption line, then it is not a mistake to compare the size of the molecule to the wavelength of the photon.
Jul
14
accepted Why doesn't Fermi's golden rule distinguish attraction from repulsion?
Jul
14
comment How can molecule of a few angstroms absorb visible light of a few hundred nanometers?
I disagree. You can learn many interesting things by learning the classical theory of electrically-small antennas (e.g. en.wikipedia.org/wiki/Chu%E2%80%93Harrington_limit ), and applying those principles to atoms interacting with light.
Jul
14
comment How can molecule of a few angstroms absorb visible light of a few hundred nanometers?
I made an animation illustrating how an electron in a superposition state moves back and forth, just like you say in the first paragraph. See en.wikipedia.org/w/…
Jul
8
answered Experimentally measuring coherence length of laser
Jul
4
accepted Can a point source be located more accurately out-of-focus or in-focus?
Jul
3
asked Can a point source be located more accurately out-of-focus or in-focus?
Jul
2
awarded  Curious
Jun
18
comment What could magnetic monopoles do that electrically charged particles can't?
There are two good questions here, incoherently mixed together. The first is: "What applications would a real magnetic monopole have?" The second is: "What applications do the magnetic monopole quasiparticles in spin ice have?" But these two questions are unrelated, see en.wikipedia.org/wiki/…
Jun
18
comment What could magnetic monopoles do that electrically charged particles can't?
Your first paragraph is describing the magnetic monopole analogue of a capacitor.
Jun
18
comment What could magnetic monopoles do that electrically charged particles can't?
The Particle Data Group article is about real magnetic monopoles (elementary particles); the ScienceDaily article is about magnetic monopole quasiparticles. They are unrelated, and it is misleading for you to suggest that they are the same thing. See en.wikipedia.org/wiki/…
Jun
18
comment What could magnetic monopoles do that electrically charged particles can't?
@WetSavannaAnimalakaRodVance -- You are misunderstanding Duality Transformations. Magnetic monopoles would behave differently than electric charges because the world is full of electrically-charged protons and electrons, which the magnetic monopoles would inevitably be interacting with. (Among other things.)
Jun
4
answered Why is the phase velocity used in the definition of the refractive index?
Jun
4
comment Why is the phase velocity used in the definition of the refractive index?
No. You cannot define index of refraction using group velocity. "Index of refraction" has a specific meaning in physics. It is a meaning that everybody learns and uses -- 100% of people, not 99%. Likewise, "group index" has a specific (different) definition. Let me ask you: "Why does the word 'velocity' always refer to the time-derivative of position, and never refers to the mass of Jupiter?" The answer is, because it's the way language works. Words have definitions. Otherwise communication would be impossible!
Jun
4
comment Why is the phase velocity used in the definition of the refractive index?
This is a strange question. If you want to talk about "c / group velocity", you call it "group index". If you want to talk about "c / phase velocity", you call it "index of refraction". It's just terminology! Those terms are as good as any. I think what you're really wondering is: "Why are there zillions of formulas that involve index of refraction, and very few formulas that involve group index?"
Jun
2
awarded  Yearling