Use this for questions relating to the proper use of physics terminology or nomenclature.
0
votes
1answer
52 views
Reason for the convention about polarization states
I'd like to know if there is a special reason for limiting convention of polarization state to waves that can be split in just two components of equal frequency.
0
votes
3answers
142 views
Is it true that an isolated fundamental particle does not decay?
Is it true that an isolated fundamental/elementary particle does not decay?
It seems logical to me.
0
votes
4answers
154 views
Isotropy and Noise
If you have a field which value is just Gaussian noise plus a constant do you call it isotropic?
there is no preferred direction
however it is not "the same" in all directions if "the same" means ...
0
votes
1answer
345 views
Wave packets v.s. wave trains
Could someone please explain the difference between a wave packet and a wave train? I have rummaged around online but have not been able to find a definitive definition.
0
votes
1answer
276 views
Energy versus free-energy diagram
Energy versus free energy diagram. I haven't been able to find an adequate definition of these two terms in relation to each other. Could someone point me in the right direction, please?
From Borrell ...
0
votes
1answer
112 views
Name for phasor model of light
I'm looking for the name of the model of light "exploring" every path to a given point, and reaching that point with a probability proportional to the square of the resultant phasor's amplitude. (Yes, ...
0
votes
1answer
83 views
What is a long-tailed distribution for physicists?
What is the most common definition of long tailed distribution for physicists? I am looking for definition and examples. Examples should have arguments why the distribution is or is not long tailed.
...
0
votes
1answer
96 views
What's the difference between these two formulas and how are these called?
I just want to know the differences between these two formulas:
$h = h_0 + v_0 t ± \frac{1}{2} g t^2$
and
$y = y_0 + v_{0y} t + \frac{1}{2} g t^2$
Also, how are these called in English?
0
votes
2answers
214 views
Are the intersections of past and future light cones spacelike?
Given a timelike reference worldline (not necessarily geodesic), we can define light-cone coordinates $\tau^+$ and $\tau^-$ so that the 3-D hypersurfaces of constant $\tau^+$ are past light cones of ...
0
votes
1answer
45 views
What is the reference spectrum?
What is the reference spectrum? I need to know how to calculate the reference spectrum of a wavelength 500nm.
0
votes
1answer
66 views
What is the pause called at the apex of an object's trajectory?
My apologies for such a basic question--I am a musician, not a physicist. But I cannot anywhere find the word, if one exists, that describes that elegant pause of an object such as a ball, thrown ...
0
votes
1answer
150 views
What is the difference between observer, frame of reference, and gauge?
It seems to me that there is considerable relationship between the three concepts: frame of reference, observer, and gauge. How do they overlap?
My current understanding is that an observer with a ...
0
votes
3answers
225 views
Is $f=ma$ an identity?
In his The Principles of Natural Knowledge, Alfred North Whitehead writes that famous $f=ma$ is an identity:
It has been popular to define force as the product of mass and
acceleration. The ...
0
votes
1answer
246 views
What's the difference between “measurement method” and “measurement procedure”? [closed]
The ISO VIM defines them as:
measurement method:
generic description of a logical organization of operations used in a
measurement.
measurement procedure: detailed description of a ...
0
votes
1answer
348 views
Metrology: What is precision for a measurement? [closed]
Is precision a "quality" of a measurement?
Is there a better (accepted by the literature) word?
0
votes
0answers
42 views
What is to be considered a “body” in physics?
Well, the question says it all; is there a definition of body in physics? What is to be considered a physical object and what it cannot?
0
votes
1answer
51 views
Conversion of ideal gas to real gas via $Z$ compression factor
The ideal gas equation $PV=nRT$ can be converted into real gas equation by compression factor $Z$ i.e $PV=Z~ nRT)$. My question is what is $Z$ and how does it arise? Is $PV/nRT$ a compression ratio of ...
0
votes
0answers
189 views
How is the term “Born level” usually defined?
How is the term "Born level" usually defined, e.g. in talking about the $pp\to Z/\gamma^*\to e^+e^-$ cross section at Born level?
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votes
0answers
213 views
What is the correct definition of “group velocity dispersion”?
When we talk about a medium with dispersion, we can define the phase velocity $v_\phi = \omega/k$ and the group velocity $v_g = d\omega/dk$. Likewise the phase index $n = c/v_\phi$ and the group index ...
0
votes
0answers
33 views
Term for “atmospheric ricochet” due to wrong “angle-of-attack”
I watched "Apollo 13" yesterday, and they had the "angle-of-attack" problem that had to be manually solved, to prevent the ship from "ricochet[ing] off the atmosphere like a rock skipping off a pond".
...
0
votes
0answers
120 views
When the p-n junction of a transistor is reverse biased? [closed]
When the p-n junction of a transistor is reverse biased?
A. current flows from the p-type to the n-type.
B. no current flows from the p-type to the n-type.
C. conduction of current occurs.
D. ...
0
votes
0answers
284 views
When is a quantity “non-physical”? [closed]
The wikipedia says
A physical quantity is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.
Formally, the International Vocabulary of Metrology, 3rd ...
0
votes
0answers
189 views
Is Photosynthetic Photon Flux Density (PPFD) a synonym for Photosynthetically Active Radiation (PAR)?
Both have units of $\mu\text{mol m}^{-2}\text{s}^{-1}$ and refer to light in the 400-700 nm range - that activates photosynthesis. However, I just want to confirm that these are synonyms and don't ...
0
votes
0answers
50 views
Taylor approximation of e(v) [closed]
Relativistic mass $\displaystyle m(v)=\frac{m_o}{\sqrt{(1-(v/c)^2}}$
$m_o$ = mass of object measured at rest
$c$ = speed of light ($3\times 10^8\;m/s$)
$v$ = speed
If the total relativistic energy ...
0
votes
3answers
2k views
Difference b/w Kinetics & Kinematics w/concrete example
(I know whether I understand this or not doesn't matter much to my work & study but am just curious.)
I still can't differentiate in my head kinetics and kinematics (similar thread is found but ...
0
votes
0answers
112 views
What is the electric field part of an EM wave? Radiation field or the induction field?
Look at this image:
I wonder if the electric field is from the induction field from a vibrating electron or the radiation field? If it is from the radiation field, as I suppose, than can someone ...
0
votes
1answer
101 views
Is reflection just a particular case of scattering?
I was talking to a colleague about optical scattering from a metallic nanoparticle, and we had a very simple doubt. If you have a particle that's small compared to the illuminated area, you can use ...
-1
votes
1answer
81 views
Is the speed of light related to the mass of the universe?
If the mass of the universe were cut in half, would it affect the speed of light?
Would it be twice as fast?
Would it stay the same?
Do we have instruments that are sensitive enough to measure the ...
-1
votes
1answer
159 views
Is a uniformly charged conducting plate the same as a uniformly charged conducting sheet?
Is it correct that a uniformly charged conducting plate is made up of two charged conducting sheets, that is, a charged conducting plate consists of four surfaces?
-1
votes
0answers
48 views
What is the difference between various fields of physics? [closed]
what is the difference between the fields of physics? like high energy physics, particle physics, cosmology, quantum physics, quantum mechanics, experimental physics, theoretical physics, applied ...
-1
votes
0answers
36 views
What is meant by cellular in the context of “cellular water”? [closed]
Paraphrased from Wikipedia:
Infrared sensing in snakes depends on a kind of natural thermography, by which tiny packets of cellular water are raised in temperature by the infrared radiation.
...
-2
votes
1answer
554 views
Can I just ask what these pulleys-and-constant-lengths problems are called?
I am not sure if this question is appropriate for this section, but I just want to know what these type of questions are called and when do physics majors learn them?
These problems have to do with ...
