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.
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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 : ...
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1answer
70 views
Does the strong (nuclear) force ever contribute to decay?
Does the strong (nuclear) force ever contribute to decay ?
Or is the weak nuclear force the only decaying force ?
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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.
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3answers
134 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:
...
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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 ...
2
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1answer
83 views
Alpha-stable isotopes
Why some isotopes with positive alpha-decay energy are stable? For example, alpha-decay energy of stable 194Pt is about 1.5 MeV.
But there is no stable isotopes with positive beta-decay energy.
...
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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 ...
1
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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 ...
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4answers
836 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 ...
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3answers
275 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 ...
1
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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 ...
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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 ...
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3answers
321 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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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 ...
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2answers
128 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
266 views
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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?
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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 ...
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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"?
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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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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
$n\to p + e + \bar{\nu}_e$?
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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 ...
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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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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 ...
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2answers
168 views
Is there a direct relationship between an isotope's neutron count and radioactivity?
In my textbook, it lists isotopes of Carbon: C-12, C-13, and C-14. It noted that C-14 is radioactive (C-12 and C-13 are not).
Is there a direct relationship between the number of neutrons and an ...
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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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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 ...
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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?
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2answers
914 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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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 ...
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3answers
5k views
What exactly is the difference between radiation and convection?
Okay, so everywhere I've read, I hear the main difference is the requirement of a medium. But for example, if you take the case of heat 'radiating' from a red-hot iron, isn't that actually convection ...
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1answer
456 views
Finding electric power generated using heat transfer
I'm working through an example I have been given to study. Suppose I have a 2m X 4m photovoltaic panel on my roof that is irradiated with a solar flux of $G_s = 700W/m^2$.
Given:
$\alpha_s = 0.83$
...
2
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2answers
345 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 ...
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2answers
546 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 ?
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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 ...
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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?
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2answers
180 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
242 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 ...
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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) ...
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1answer
227 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 ...
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1answer
254 views
Does neutron radiation form clouds?
I've heard a couple of scary stories from experienced accellerator physiscists about something called neutron clouds. Apparently, if you have an experiment like a fixed-target experiment that produces ...
5
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4answers
364 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 ...
8
votes
3answers
501 views
Can two spaceships go fast enough to pass straight through each other?
Probability of interaction between two particles tends to wane with increasing energy. Technically, the cross section of most interactions falls off with increasing velocity.
$$\sigma(v) \propto ...
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0answers
47 views
Light vs. X-ray interactions with Phosphor
Looking for some information on how light and xrays interact with phosphorous, or what might cause the following:
Scenario
A focus beam of light is directed at a phosphor plate at the same time as ...
2
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0answers
186 views
How is the “negative dispersion” derived?
I'm looking at Kopfermann H., Ladenburg R., Nature, 122, 338-339 (1928) and it appears Ladenburg in Ladenburg R., Z.Physik, 4, 451-468 (1921) was the first to discover the phenomenon of "negative ...
2
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1answer
111 views
Does magnetic geometry determine the scaling of a Polywell fusor?
Does magnetic geometry determine the scaling of a Polywell fusor?
Forgive imprecise terminology here - by "magnetic geometry" I mean the configuration of the magnets, the configuration that creates ...
2
votes
4answers
436 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, ...
3
votes
2answers
217 views
Where does the excess energy emitted by a microwave go?
If there is nothing in the microwave, where does the excess radiation go?
Why doesn't the radiation accumulate and blow it up?
Should I cook two pieces of Canadian Bacon twice as long as I cook one?
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2answers
491 views
Maximum electron momentum in $\beta^-$-decay
This should be easy, but I think I have a mind-block...
For $\beta^-$-decay, what is the maximum possible momentum for the electron? The two equations I can use are conservation of energy and ...
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1answer
124 views
Radiation dosage problem [closed]
A large room is filled with air polluted with Caesium-137 at an average density of 1 Cs-137 particle per $\text{cm}^3$. A human is sitting inside the room for duration of $T$. What is the total energy ...
