Radiation is a process in which energetic particles or energetic waves travel through a medium or space. The particles or waves radiate (i.e., travel outward in all directions) from a source.
2
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2answers
286 views
Has Bose-Einstein theory been considered for dark matter?
Has Bose-Einstein theory been considered for dark matter?
The theory would explain why no measurable radiation is emitted due to zero temperature--its lack of interaction with other matter and its ...
3
votes
4answers
475 views
How do electrons jump orbitals?
My question isn't how they receive the energy to jump, but why. When someone views an element's emission spectrum, we see a line spectrum which proves that they don't exist outside of their orbitals ...
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1answer
56 views
Does it happen at high energies (heavier leptons decay)?
A lepton is an elementary particle. The best known of all leptons is the electron which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties.
The ...
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0answers
37 views
Non reflecting boundaries in waveguides
Can someone please explain the Sommerfeld radiation condition and what is the alternative non-reflecting boundary conditions for waveguides of general geometries?
3
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2answers
289 views
How to interpret Stefan-Boltzmann's law?
The Stefan-Boltzmann equation states $e=\sigma T^4$, but how do we interpret this?
Is this completely wrong: A body of size $s^2$ generates the radiation/temperature $T^4$ for a given size and a ...
1
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0answers
32 views
Effect of Background Radiation on a Transmitted Signal
I'm coding a basic simulation of using error correcting codes to transmit data from a satellite back to earth. I'm not sure what to set the "noise level" to. Let's say a satellite orbiting Mars ...
1
vote
0answers
28 views
Half-Life Question [duplicate]
Possible Duplicate:
How do we know that some radioactive materials have a half life of millions or even billions of years?
I understand how to calculate decay, but it seems to me that the ...
5
votes
4answers
363 views
Interpretation of Wigner function in optics
I work in the field of synchrotron radiation sources where radiation (often x-rays) is produced from an electron beam going through magnetic fields. The quality of the resulting x-ray beam is ...
1
vote
2answers
111 views
How to detect radiation on the metal (coin)?
I've got metal coin : http://www.worldpeacecoin.org/
Ruble/dollar, a coin of disarmament with certificate. But, I am very spleeny person, I fear of it's radiance level and I don't know if I can trust ...
2
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1answer
49 views
Range of electromagnetic waves
I was reading this article. There is a statement "It is a well-known fact that the telecom towers mounted with antennas in the lower frequency bands can cover far greater areas than those using the ...
4
votes
1answer
1k views
What common materials can effectively block infrared radiation?
I have a plastic container and want to make sure that infrared radiation (specifically, in the 750-850 nanometer range) cannot pass through it. Would wrapping it in aluminum foil do the trick? If not, ...
0
votes
1answer
108 views
How to choose a $\alpha$, $\beta$, $\gamma$ measurement detector?
There are many different detectors for different radiation,such as NaI,HpGe,CsI for $\gamma$ detection,and ionization chamber,proportional counter,Geiger counter for $\alpha$, $\beta$ detection,but ...
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0answers
57 views
Which of the following radiation measurement devices is suitable to measure the radiation level in a Data Center? [closed]
Which of the following radiation measurement devices is suitable to measure the radiation level in a Data Centre?
Geiger Mueller (GM) Detectors with Pancake Probes
Alpha Radiation Survey Meter
...
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2answers
170 views
Where does the “borrowed energy” come from in Alpha decay?
I was also thinking about the uncertainty principle in regards with energy & time. The question of something like:
Alpha tunneling out of the nucleus is where this can be invoked, but having an ...
0
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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
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0answers
18 views
Is there a way to compute or explain if a decay prefers decaying into mainly mass or mainly energy?
Is there a way to compute or explain if a decay prefers decaying into mainly mass or mainly energy ?
I know quarks prefer to decay into the most massfull quarks : ...
1
vote
3answers
132 views
How to detect Iodine 131?
I 131--->β 333.8kev(7.27%)--->γ 636.989kev(7.17%)
I 131--->β 606.3kev(89.9%)--->γ 364.489kev(81.7%)
(you can also check the them here:
...
3
votes
4answers
197 views
Possibility for radiation in dark matter that is not interactive with regular matter?
Definition: Radiation in this case does not refer to electromagnetic radiation. It refers to any kind of emission of energy, even energy that does not interact with regular matter.
Just like dark ...
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1answer
224 views
How is tritium illumination possible without negative health effects?
Turns out there's tritium illumination - a tiny very strong plastic tube will be covered in phosphor and filled with tritium. Tritium will undergo beta decay and a flow of electrons will cause the ...
1
vote
1answer
52 views
References for nuclear masses, mass deficits, decay rates and modes
Where can I find the base data for computing the energy release of nuclear decays and the spectra of the decay products?
My immediate need is to find the energy release by the beta decay of Thorium ...
0
votes
3answers
274 views
How can there be heat in a vacuum?
I keep reading in the Physics World focus issue on vacuum technology about scientists creating high temperatures in the vacuums etc.
If heat is caused by thermal energy being radiated from particles ...
0
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0answers
48 views
What sort of thin film experiments can be done in zero gravity and in the presence of cosmic radiation?
I recently found out about sending stuff into space and using the unique zero gravity and cosmic radiation riddled environment to investigate stuff like crystal growth. Since thin film science is a ...
2
votes
4answers
433 views
Why do electron-positron pair annihilate upon contact?
I'll a appreciate a layman's explanation, if there exists one, to this question that arose when reading an popular-science level article on Einstein and the $E=MC^2$ equation.
What I mean is that, ...
1
vote
2answers
210 views
Antimatter bomb
I stumbled upon this wikipedia article on antimatter weaponry.
Being greatly appalled by the sad fact that large sums of money are being wasted on this, I could not stop myself from thinking for a ...
1
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4answers
817 views
Why is Neutron Heavier than Proton?
This is Neutron decay:
$$n^o \to p^+ + e^- + \overline {\nu_e}.$$
and this is proton one:
$$p^+ \to n^o + e^+ + \nu_e$$
so when the $e^+ =e^-$ and $\nu_e=\overline {\nu_e}$ why $n \not= p$?
my ...
0
votes
1answer
69 views
At what rate does radiation exposure occur at high-c speeds?
If a future astronaut travelled to Alpha Centauri at a significant percentage of light-speed?
Apart from increased blue shifted radiation from their direction of travel - how would they experience ...
5
votes
3answers
319 views
What is happening over the 15 minutes it takes a neutron to decay?
I've read that free neutrons decay into a proton, electron and neutrino with an average lifespan of about 15 minutes. Is there anything physically different about a neutron that has existed for 14 ...
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2answers
301 views
Transient radiation--heating a slab
Hey guys I really need help on this problem.
A ceramic slab of dimentions 5cm x 10 cm x .25 cm has to be heated to $177\,^{\circ}{\rm C}$. The ceramic slab travels on a conveyor belt traveling at ...
0
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2answers
126 views
How is a cathode ray tube different from beta minus radiation?
In beta minus the result is one neutron in the nucleus changing to a proton, plus an electron and an anti-neutrino being sent off.
The antineutrino is indifferent to our health. So I guess what ...
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2answers
264 views
1
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0answers
93 views
How do I calculate the Radiation length of a Molecule
I want to calculate the Radiation length in a Molecule with the Formula given on wikipedia. How do I calculate Z and A for a molecule to put it into the Formula?
2
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0answers
42 views
A problem concerning the change of temperature and spectrum of a filament
http://www.flickr.com/photos/83373487@N04/7636968446/in/photostream
The spectrum of a filament is given before, the left one have the lowest tempreture, the middle has the medium and the right one ...
2
votes
2answers
81 views
Can a free hydrogen atom constitute ionizing radiation?
Radiation is basically just particles flying around, right? Are free hydrogen atoms just typically not moving fast enough to be considered "radiation"?
2
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0answers
53 views
Are scalars starting at around 1300 MeV analogous to some kind of sound in the vacuum glue?
Are scalars starting at around 1300 MeV analogous to some kind of sound in the vacuum glue?
Background:
There are scalars starting at around 1300 MeV which are probably some combination of ...
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1answer
99 views
Radiative transfer equation solution
The solution of the radiative transfer equation for spherical ionized blob :
\begin{equation}
\frac{dI_{\nu}}{ds} = j_{\nu}-\alpha I_{\nu}
\end{equation}
and solution is (Ref: ...
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vote
3answers
167 views
Neutron decay and electron anti neutrino $n\to p + e + \bar{\nu}_e$
Why do we need neutrino to explain neutron decay?
Is there any evidence regarding existence neutrinos in the context of
$n\to p + e + \bar{\nu}_e$?
1
vote
2answers
72 views
$\Omega_{r}$ from WMAP results?
To do some Friedmann-Lemaître cosmology calculations, I would like to know an estimation of $\Omega_{r_0}$ ($\Omega$ radiation today). WMAP 7 give estimation of $\Omega_{b}$, $\Omega_{c}$ and ...
1
vote
1answer
106 views
How do gravitational waves sustain and propagate large scale spacetime curvature?
I understand that gravity in GR is a manifestation spacetime curvature dictated by the field equations by the principle that objects follow the geodesic path in spacetime.
And, I get how ...
4
votes
3answers
364 views
Cosmic ray hazards
The Pierre Auger Observatory site mentions the detection of a 3E20 eV (48 J) cosmic ray whose energy, well above the GZK cutoff, was based on an analysis of its atmospheric shower. This was equivalent ...
8
votes
2answers
1k views
Why are alpha particles made of 2 protons and neutrons?
When experiencing alpha decay, atoms shed alpha particles made of 2 protons and 2 neutrons. Why can't we have other types of particles made of more or less protons?
2
votes
2answers
907 views
How to calculate gamma radiation shielding?
A device emits 0.2 μSv/h of gamma rays. How thick does an aluminum sheet need to be to completely stop radiation from coming out ? What equation is to be used to calculate this ?
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votes
1answer
1k views
Why are umbrellas black?
Why are umbrellas specifically in black? Of course we do have colored ones, but black is the majority. Is there any scientific reason behind it?
5
votes
2answers
544 views
“Dear radioactive ladies and gentlemen” - Letter by Wolfgang Pauli
In 1930, Wolfgang Pauli wrote a letter to Lise Meitner for a convention in Tübingen, considering the problem of beta decay.
Does anybody know, where to find the original letter online ?
2
votes
2answers
344 views
Why does a microwave oven affect other electronic devices
When I turn my microwave oven over the stove on, it will cause a motion sensor light in the hallway next to the kitchen to got off and on. This affect can be reproduced anytime. I did notice that ...
0
votes
0answers
49 views
Problem on nuclear physics radioactivity [duplicate]
Possible Duplicate:
How do we know that C14 decay is exponential and not linear?
Please help me solving this problem.
Find the half life period of uranium-238,if one gram of it emits ...
2
votes
2answers
178 views
Can x-ray radiation be compared to background radiation?
I've been trying to learn about the possible effects of x-ray radiation from dental x-rays and most of the resources I come across compare the exposure to that of natural background radiation.
...
2
votes
1answer
241 views
Steady State Temperature of an Object Orbiting the Earth
This may be irrelevant or stupid to ask but I couldn't come up with a good answer. At least, we could not agree on with my friend the other day.
I would like an estimate of the temperature of a human ...
0
votes
2answers
216 views
Reconstruction of information stored in an evaporating black hole from the emission spectrum?
For simple setups, where the radiation field deviates not too far from thermodynamic equilibrium (< 10 %), corrections to the Planckian thermal emission spectrum can be calculated (and measured) ...
1
vote
1answer
225 views
Absorption / Control / Reduction of EMF radiation using passive antennae & matched load
Wanted to understand the physics behind usage of passive antennae and matched load combination, to absorb, control and reduce the Electromagnetic-Field (s.a. due to microwave radiation from cellular ...
2
votes
2answers
217 views
What is the risk from radiation on imported food from Japan
I'm currently resident in Hong Kong a country which appars to import heavily from Japan.
Last saturday 7th May I went to a restaurant:
http://www.openrice.com/english/restaurant/sr2.htm?shopid=39760
...
