6,137 reputation
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bio website sjbyrnes.com
location Massachusetts
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visits member for 3 years, 2 months
seen 5 hours ago

18h
answered Extracting heat energy without a heat engine
Aug
15
comment Ray Tracing and Combination of Lenses
In this comment you acknowledge (correctly) that if the second lens is strongly diverging, then it prevents the light from coming to a focus, i.e. D rather than B. But your answer still says that B is the right answer. The only way you can say that the answer is B, is to say that D is a special case of B, which I do NOT think is a reasonable interpretation of those sentences in common parlance. I think that the correct answer to the question is not B, it's "Either D or B, but there isn't enough info to decide."
Aug
15
comment Ray Tracing and Combination of Lenses
You wrote "The answer is c, saying that the focus point will be further away". Please double-check. That's not what c says.
Aug
4
awarded  Civic Duty
Jul
21
answered “Lack of inversion symmetry” in crystal?
Jul
21
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.)