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Just here to learn and share.


Jul
28
comment What is the logarithm of a kilometer? Is it a dimensionless number?
It is also worth noting that a trigonometric function ought to applied in the same way, i.e. to unitless numbers. Otherwise, it does not make physical sense.
Jul
28
comment Pendulum period of different masses
When you analyze $\tau = I\alpha$ for a pendulum undergoing small oscillations, you will find that the mass terms cancel on both sides and hence the period does not depend on mass of the pendulum.
Jul
28
comment GHz rate single photon counting
@dmckee I don't think subtraction will work well for NIR ones. At least the ones we used were not good enough at 860nm. We switched to PerkenElmer photon counting modules instead.
Jul
27
comment GHz rate single photon counting
Don't PMT's have serious dark current issues (unless cryogenically cooled)?
Jul
26
comment Any physical example of an “explosive” differential equation $ y' = ky^2$?
A "drag" force that is used to approximate motion of a body in a fluid, (i.e $F=kv^2$) is the first example that comes to my mind.
May
18
comment What is the optical power level of common fiber optics lasers?
To my limited knowledge, NL effects are a concern and manifest as pulse distortion (due to many competing effects). They are more pronounced when the pulse width is short (100ns perhaps?). This effectively puts a limit on useful bandwidth. I vaguely remember analysis using an eye-diagram to quantify the effect of distortion.
May
15
comment Light Ray Reflection from concave mirror
Removed the ridiculous down-vote by adding a +1.
Mar
20
comment Couldn't we measure electrons with good enough technology?
In my understanding, a measurement necessarily involves an interaction, and thinking simplistically, electrons interact with other electrons by exchanging photons. In theory you could have a device 'tuned" to some other interaction, then perhaps you don't have to detect photons. By measure I presume you wish to measure position? The question is not very clear.
Jan
6
comment Eliminating IR light reflection perceived by a steep viewing angle
The easiest way to accomplish your goal is as you said, add an IR filter to your camera. I would pick an "'interference" filter (eoc-inc.com/infrared_filters.htm).
Jan
5
comment Connection between quantum physics and consciousness
As far as I can tell, there is no logical definition of consciousness that compatible with physics.
Dec
31
comment Why can't a spaceship accelerate for ever? Since there is no friction in space
There could be magnetically induced drag that can occur when a conductor moves in an external magnetic field.
Dec
28
comment Can you speed up radioactive decay of plutonium?
@RichartBremer, what if the rocket blows up during launch?
Dec
28
comment Why do we classify states under covering groups instead of the group itself?
A group is an abstract mathematical object. Measurements/Experiments are in the real field. So, if you want to draw meaningful conclusions that you can verify experimentally, you have to work with operator representations (in $\mathbb{R}$) that are appropriate. Ultimately, if you cannot prove something (or its consequences) that can be experimentally verified, it is worthless. While this does not directly answer your question, I think it is a useful reminder on why we work with representations instead of abstract objects. Hence the comment.
Dec
26
comment The two faces of $F = m*a$
It should be noted that only an external force can change the momentum of the system. There is some ambiguity here as one must first define the system of interacting objects.
Dec
23
comment Integration question from book “e: The Story of a Number” by Eli Maor
Make the change of variable in eq 3 as: $g-av=z$, then differentiate both sides and express the left hand side in terms of the new variable $z$.
Dec
23
comment Is the superposition principle universal?
I have to disagree with that. In fact the closure property of a group is the fundamental principle at play. The principle of superposition is antiquated and anybody who studies group theory will tell you that it is unnecessary terminology. The "+" can be replaced by another operation say $\diamond$. The point is, you have to decide which is the strong and which is the weak operation when you build a field from a group and two operations.
Dec
23
comment Circular polarization: properties and detection
There are a couple of things to consider. In your detection measurements, you are looking at energy, so polarization states are degenerate in this measurement. Polarization degree of freedom carries (loose terminology) angular momentum and a direct measurement of the angular momentum can be easily seen in light-matter interactions (my experience). To distinguish between polarizations, the easiest way is by using a high quality crossed polarizer arrangement. What wavelength are you working with?
Dec
23
comment Thermal imaging camera
Removed the -1 by adding a +1. Can you please stop the ridiculous drive by negative voting???
Dec
23
comment Is the superposition principle universal?
I think we are speaking of different things. In nonlinear interactions, you are dealing with tensor spaces, which does not change the fact that the abstract field operations do not change.
Dec
23
comment Is the superposition principle universal?
Vladmir, what is the specific problem? Please check my comment above and see if it clarifies matters (a bit).