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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$\beta^+$ decay
We've been discussing radioactive decay at school, and I grasped everything except for $\beta +$ decay. When I googled radioactive decay, I immediately found out they dumbed down radioactive decay for ...
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769 views
Decay of massless particles
We don't normally consider the possibility that massless particles could undergo radioactive decay. There are elementary arguments that make it sound implausible. (A bunch of the following is ...
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765 views
Why some nuclei with “magic” numbers of neutrons have a half-life less than their neighbor isotopes?
It's easy to find the "magic" numbers of neutrons on the diagrams of alpha-decay energy: 82, 126, 152, 162. Such "magic" nuclei should be more stable than their neighbors.
But why some nuclei ...
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6answers
779 views
Is there any thing other than time that “triggers” a radioactive atom to decay?
Say you have a vial of tritium and monitor their atomic decay with a geiger counter. How does an atom "know" when it's time to decay? It seems odd that all the tritium atoms are identical except with ...
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Laptops in space
I was reading an article regarding the Shuttle's GPCs and how they stack up against commercially-made hardware on http://www.nasa.gov/mission_pages/shuttle/flyout/flyfeature_shuttlecomputers.html and ...
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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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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 ...
8
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4answers
177 views
Why are alpha particles such a prominent form of radiation and not other types of nucleon arrangement?
It is said in many textbooks that alpha decay involves emitting alpha particles, which are very stable. Indeed, the binding energy (~28.3 MeV) is higher than for $Z$-neighboring stable isotopes. But ...
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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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2answers
517 views
Is it Possible to Determine Radiation Levels Using Satelites?
Given recent events in Japan, this got me wondering. Is it possible to determine radiation levels reliably not having Geiger counters near the possible radiation contaminated zone? According to ...
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3answers
1k views
Would wearing clothing that is black on the inside and white on the outside keep you cooler?
The Straight Dope ran an explanation of why nomads often wear black clothing - it absorbs heat better from the body. On the other hand, white clothing reflects sunlight better. Is it possible to get ...
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4answers
600 views
Can you speed up radioactive decay of plutonium?
We all know the issue of deep geological repositories for fuel rods. Is there a way to speed up the rod's decay to render them harmless in less than 10 years?
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607 views
Why doesn't orbital electron fall into the nucleus of Rb85, but falls into the nucleus of Rb83?
Rb83 is unstable and decays to Kr-83. Mode of the decay is electron capture. Rb85 is stable.
The nuclei Rb83 and Rb85 have the same charge. Rb85 is heavier than Rb85, but gravitation is too weak to ...
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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 ...
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2answers
547 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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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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3answers
240 views
Is there a way to decrease the rate of nuclear Beta decay?
In that question and its answers it was mentioned that you could trigger radioactive decay by bombarding atoms with gamma rays of the right energy level (there may be other solutions I do not know ...
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2answers
347 views
Sunflowers and radioactivity
I read yesterday that sunflowers were used and to cleanup radioactivity at Chernobyl and the Atomic Bomb sites in Japan and may be used as part of a campaign to clean up the Fukushima area.
But my ...
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2answers
512 views
What other shielding material than lead is effective against gamma rays?
As the question in the title states I am wondering what material can be effectively used to shield gamma rays apart from lead? I believe concrete is often used, but it is nowhere near as effective as ...
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2answers
704 views
Tunneling of alpha particles
Consider this explanation of the alpha decay: It says
The Coulomb barrier faced by an alpha
particle with this energy is about 26
MeV, so by classical physics it cannot
escape at all. ...
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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 ...
5
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1answer
146 views
Oort Cloud Detection
The hypothetical Oort cloud is an explaination for long period comets. It presumably is made up of icy bodies orbiting up to 50,000 AU from the Sun. If so, shouldn't the Spitzer IR telescope have ...
5
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1answer
557 views
What temperature can you attain with a solar furnace?
A solar furnace is a device that concentrates the sun's light on a small point to heat it up to high temperature. One can imagine that in the limit of being completely surrounded by mirrors, your ...
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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 ...
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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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1answer
130 views
Radiation exposure to a child who was briefly in the presence of an adult who had received a 18FDG PET scan
I am a physician who thought she was good at math, but apparently am not as I cannot figure out this mathematical/physics question. (My background is obviously NOT nuclear medicine!) A family friend ...
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2answers
492 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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5answers
303 views
Without a reactor vessel breach, how does radiation build-up in containment buildings of troubled nuclear reactors?
It seems that at Three Mile Island and in Fukushima, there was a build-up of radioactive gasses, and other gasses like hydrogen in the containment buildings.
Wikipedia says: The containment ...
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1answer
103 views
What is the difference between Radiation and Electromagnetic Radiation
Are the two equivalent or is Electromagnetic Radiation a subset of Radiation. I am further confused by the fact that electromagnetic radiation includes both ionizing and non ionizing types of ...
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1answer
54 views
$\alpha$ decay to more than one nuclear state
I do not understand how $\alpha$ decay can be a probabilistic process such that there are multiple products from the decay. For example:
$^{241}\mathrm{Cm}$ decays to the excited states of ...
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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, ...
4
votes
1answer
274 views
Transverse current equivalence in Coulomb gauge
I have a question concerning transverse (solenoidal) current in the Coulomb gauge. This current is the one that enables the radiation, since we have a wave equation for the vector potential:
...
4
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1answer
184 views
The most stable metal for radioactive environment
Could you suggest which metal/alloy shows the least activation & better long-term stability for space (LEO, inside Van allen belts, deep space) applications?
Or stability of construction ...
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3answers
442 views
Are these radioactive particle matter and air emmissions dangerous, 2000KM from Fukushima?
I have 2 questions, as a expat and new parent residing in Shanghai (2000km from Fukushima) where we are now experiencing radioactive fallout from the Fukushima Nuclear Plant (Japan), we can not get ...
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4answers
484 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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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
580 views
What is the required thickness of concrete needed to entomb a leaking reactors emissions?
What is the minimum thickness of an aggregate concrete membrane to prevent radioactive particles from escaping a broken reactor?
I am interested in calculating the amount of concrete required to ...
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1answer
295 views
Kinetic energy of alpha-particle in $^{212}$Po decay
Admittedly, Nuclear Physics is not my strength. I'm writing a simulation to model alpha-decay. So far, I have looked up the values of the kinetic energy of the alpha particles that are emitted in a ...
3
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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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1answer
40 views
Is a beta decay possible with out the emission of an electron in the process?
Is a beta decay possible with out the emission of an electron in the process ?
Beta decay involves the formation of a proton and an electron from a neutron.
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2answers
291 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 ...
3
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3answers
217 views
Ratio of radiation sources in the uranium cycle
Sorry, I know y'all are probably getting a lot of questions re: Fukushima, but I had a very specific one and no-one has been able to answer it.
I am specialised in medical radiation, and have been ...
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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
...
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2answers
126 views
Would a laser with four possible energy levels be better than three?
I'm wondering about achieving population inversion for a laser. I learned that without an active medium, it's not possible to create a laser with only two energy levels, but it would be possible with ...
2
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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
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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"?
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, ...
2
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2answers
503 views
Can extra-solar gamma rays reach the Earth's surface?
Can gamma rays of high enough energy entering our planet's atmosphere reach the surface (50% probability)?
Or, in other words, is there a window for extremely high-energy gamma rays like for the ...
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2answers
60 views
Is it possible to record the 'blue air" effect when a core goes critical?
I've been studying about radiation, and I saw something called the Demon Core. Apparently, it was a core that was under experimentation by the government in Los Alamos to see the exact point at which ...
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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 ...
