7,510 reputation
1333
bio website sjbyrnes.com
location Massachusetts
age
visits member for 3 years, 6 months
seen 2 days ago

Feb
5
comment How much lift does the average latex helium filled party balloon produce?
The helium is under higher pressure than the air, being squeezed by the rubber, but this probably makes a negligible difference. OTOH, I'm not so sure it's OK to neglect the weight of the rubber itself. Is it much less than 14g? I don't know.
Feb
1
comment No magnetic field from a static charge - Is there a simple physical argument to show why?
@Chris -- It is not true that "magnetic fields can only be caused by time varying electric fields". One counterexample is a loop of wire carrying a DC current. Another counterexample is an electron at rest (since it's at rest, its electric field is not changing over time).
Jan
22
revised statistics for photon counts in photomultiplier
clarify that poisson statistics are almost always correct; add more clearly how probabilities relate to poisson statistics
Jan
21
answered statistics for photon counts in photomultiplier
Jan
20
comment Do electrons in multi-electron atoms really have definite angular momenta?
It might indeed be small, but why is it small? One naively expects total e-e repulsion to be comparable to e-nucleus attraction, right? (I expect that my question has one answer for lithium and a different answer for uranium.)
Jan
20
comment Do electrons in multi-electron atoms really have definite angular momenta?
Hartree-Fock assumes that the multi-electron wavefunction is a single Slater determinant (in the 1-electron wavefn basis), rather than the sum of multiple Slater determinants. Your answer raises the question: To what extent is that true for light atoms and for heavy atoms? I don't know.. Another thing that OP may have been thinking of was the prescription for calculating a ground-state term symbol -- en.wikipedia.org/wiki/Term_symbol#Ground_state_term_symbol -- I always figured the prescription was more-or-less a mnemonic, not a literal description of the electrons. But I don't know.
Jan
18
comment Can light be canceled by merging with an inverted wave?
Possible duplicate: physics.stackexchange.com/questions/23930/…
Jan
16
comment No magnetic field from a static charge - Is there a simple physical argument to show why?
Whatever arguments people put forth will hopefully not be inconsistent with the fact that an electron at rest DOES have a magnetic field. :-D
Jan
11
answered Is infrared light diffused on walls?
Jan
8
comment Current through the reverse biased junction in transistor
You can try William Beaty's discussion: amasci.com/amateur/transis.html
Jan
7
answered Apparent paradox in equation of continuity
Jan
7
revised Apparent paradox in equation of continuity
improve english wording and grammar
Jan
4
answered Question on Total, Orbital and Spin Angular momentum
Jan
3
answered laser pointer class III and potential eye damage
Jan
2
awarded  Organizer
Jan
2
revised Origin of Laue equations?
add history tag
Dec
16
answered Optical equivalent of a superconductor
Dec
15
comment What is the color of Water?
This answers the question well, but it is worth clarifying that pure water really is a blue substance. It's only slightly blue and it's hard to see the blue tint in a small thickness of water, like a glass of water.
Dec
7
comment Is energy the ability to do work?
@KabeloMoiloa -- You're asking "Why do high school physics teachers and physics textbooks occasionally say things that are incorrect?" I am not in a good position to answer that. Probably many factors are involved. Understanding the education system is even more difficult than understanding energy, in my opinion!! :-P
Dec
5
revised Is energy the ability to do work?
added 2201 characters in body