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bio website sjbyrnes.com
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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
Dec
5
answered Is energy the ability to do work?
Dec
5
comment Splitting light into colors, mathematical expression (fourier transforms)
It doesn't sound like filtering or fourier transforms are at all relevant here. Just multiply (total number of photons) * (fraction of photons that are red) = (number of red photons). [The filtering or fourier transforms would be used if you only knew the electric field as a function of time, but it doesn't sound like that's the case. It sounds like you know the rate of photons as a function of position.] Don't make a simple thing complicated!
Dec
3
comment Why isn't temperature measured in units of energy?
See also my answer to a related question: physics.stackexchange.com/questions/17551/units-and-nature/…
Dec
2
answered Ejected Electrons with 0 KE?
Nov
23
comment How is Gauss' Law (integral form) arrived at from Coulomb's Law, and how is the differential form arrived at from that?
While it's healthy to know these derivations, you should keep in mind that Gauss's law is more general than Coulomb's law. Coulomb's law is only true if the charges are stationary, there are no changing magnetic fields, etc. But Gauss's law is true under all circumstances. So Gauss's law is more than just a consequence of Coulomb's law.
Nov
20
answered Using the monte carlo method to compute the magnetic field of a curent carrying loop
Nov
13
comment What is the approximate electrical conductivity $\sigma$ of graphene in S/m or S/cm?
If I assume the few-layer graphene in the Novoselov paper is actually 3 layer graphene (just a guess), then the graphene is 1nm thick, and with a strong gate its sheet resistance is 200 ohm/square. If we pretended that you could make 1nm thick copper without changing the resistivity, its sheet resistance would be 20 ohm/square. So I guess you could say that copper is 10X more conductive than graphene, at least in this particular paper. But it seems to me that this is comparing apples and oranges. [Note: This comment replaces a previous version I just deleted where I misread the graph scale.]
Nov
8
comment When I connect in series two floating capacitors, one charged and the other not charged, does current flow?
There is a rule: The charges on the two plates of a capacitor must be equal and opposite, and no (net) charge can be anywhere except the plate of a capacitor. When stray capacitance is very small -- usually the case -- this rule is very strictly enforced. No charge can flow from 2 to 3 without violating the rule: Either the charge on 3 will NOT be equal and opposite the charge on 4, or else charge will appear on the open lead connected to 4.
Nov
5
comment What software programs are used to draw physics diagrams, and what are their relative merits?
It is only fair to mention that matplotlib is extremely similar to MATLAB: Similar user interface, similar capabilities, similar default styles, etc. One advantage of Matplotlib over matlab is that you get to use python, which is a better programming language than matlab. Another is that matplotlib is free, while matlab is prohibitively expensive unless you get it through work or school or pirated. On the other hand, MATLAB has better help files, easier installation, and a bigger scientific user base [but I hope those things will eventually change.]
Nov
5
comment What common materials can effectively block infrared radiation?
It is worth noting that even when the reflection is not quite 100%, that doesn't mean light can pass through the aluminum foil. The rest gets absorbed, not transmitted. (Unless the aluminum is under ~50 nanometers thick, for visible and near-IR!)
Oct
26
answered Reflectance vs. Thin Metal film Thickness Graph
Oct
12
comment Dependance of temperature on color of metals
How do you know that the heating of cars in sunlight is dominated by the windows?? This is not obvious to me. Also, different paints may have more or less radiative cooling - especially important at night. There again, it's not obvious that the windows are more important than the paint. Personally, I wonder whether Klein's comment is actually true.
Oct
5
comment Does Nantenna (nano antenna) violates 2nd Law of Thermodynamics?
I would bet a large sum of money that the overwhelming majority of professional physicists would agree with my assessment that the device cannot possibly work as advertised in the application in question, because if it worked then it would violate the Second Law. However, I have not actually done a survey!
Oct
5
comment Does Nantenna (nano antenna) violates 2nd Law of Thermodynamics?
I am the one who put those words into the wikipedia article. What I wanted to say was: "Obviously this application would violate the second law of thermodynamics." But I ended up writing that more understated and diplomatic sentence which you quote, because of wikipedia's referencing rules. Indeed, if you have a room at temperature T, and a nantenna device at the same temperature T, it cannot charge a battery. This is a textbook example of the Second Law.
Oct
3
comment Liquid crystal shutter with >90% transmission?
Agree. The 50% limit is sacrosanct as long as there is unpolarized light to start, and at least one polarizer in the system. If I had to guess, the "90%" quote is actually shorthand for "90% of the theoretical limit" -- i.e. 45%. Especially if it was a brief offhand remark, it may have been misunderstood!
Sep
21
revised Why is torque not measured in Joules?
clarify wording in third paragraph
Sep
21
answered Why is torque not measured in Joules?