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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How did Lyman discover his series?

How did Lyman discover his series in hydrogen atom? How did he know that the final energy level is the first level and not the second or the third or etc.? Or how did the other scientists know which ...
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Do human bodies give off a consistent but unique radiation/electromagnetic/energy signature?

Is there any facet of the energy emitted by a human body that is consistent and unique - like a fingerprint, but a signal that could be detected by a remote device?
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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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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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920 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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801 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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142 views

Does any lower frequency electromagnetic radiation naturally reach us from the Sun?

I am not sure whether the sun originally emits everything in the electromagnetic spectrum, (whatever the relative strengths of each portion might be), but I do read that many waves, including gamma / ...
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68 views

Optically thick media

What does "optically thick media" mean? Does this property depend on the length of an enclosure? Why is the diffusion approximation for the radiative transfer equation applied to optically thick ...
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610 views

How is the Earth heated by a Full Moon?

While the moon is certainly not a good reflector of solar radiation, surely the radiation it reflects back heats the Earth (even if it is a terribly small amount). How would one go about calculating ...
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406 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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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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429 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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335 views

Why doesn't a nuclear fuel pool become irradiated?

Why doesn't the volume of water in a nuclear fuel pool become irradiated? Why wouldn't the water around the pool become radioactive and circulate around making the whole thing deadly? My question ...
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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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88 views

Energy balance for beta decay of cobalt-60

I am confused by a simple fact about the $\beta^{-}$ decay of ${}^{60}{\rm Co}$ nucleus. According to Wikipedia, the most likely decay branch is to an excited state of ${}^{60}{\rm Ni}$, see the ...
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241 views

One way insulation?

I know from basic physics lessons that a box painted black will absorb heat better than a box covered in tin foil. However a box covered in tin foil will lose heat slower than a black box. So what ...
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74 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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554 views

Why does positronium decay into 2 photons more often than into 3 photons?

I cannot find the answer to the above question. I know that para-positronium is created with a probability of $25\%$ and decays into 2 photons, while ortho-positronium is created with a probability ...
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144 views

Acceleration of electric charges and radiation

According to classical electromagnetic theory, accelerated charges should emit radiation and lose energy. The reason given in my book why atoms don't emit radiation (say, when the atom moves along a ...
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137 views

Soft Bremsstrahlung: why $\hat{k}\cdot\mathbf{v}= \mathbf{v}'\cdot\mathbf{v}$?

On page 181 in Peskin & Schroeder they say that we consider the integral (intensity) $$\tag{1}\mathcal{I}(\mathbf{v},\mathbf{v}') = ...
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378 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: ...
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193 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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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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Modeling incoming solar radiation

I want to write a model for estimating incoming solar radiation for a specific latitude on earth but I am struggling to find an appropriate source which shows the required equations for doing so. ...
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656 views

What is the shielding in nuclear reactors mainly against?

I have a little knowledge about ionizing radiation and I have been confused over why nuclear reactors need these massive shields. So, if I am not mistaken, Alpha and Beta radiation are not that ...
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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 ...
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135 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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Background radiation: radon vs potassium 40

In doing a little research into natural background radiation, I came upon a table from the National Council on Radiation Protection and Measurement (NCRP). It shows that inhaled radon gas is by far ...
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Radiation: Inverse square law

Gamma radiation follows the inverse square law, I understand this as "double the distance, quarter the intensity" So if you have a gamma source, at the source (distance = 0), the Intensity is $I_0$, ...
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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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How can we detect cosmic background radiation?

From what I understand, CMB is the left over radiation from the Big Bang. As all matter, including the Earth, was made during the Big Bang and then as the universe expanded that matter/energy got ...
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How can scintillation gamma-spectrometers work given that track length is different for different angles?

As far as I understand, the basic principle of gamma spectrometer is simple - gamma ray hits scintillator, it generates number of photons which roughly proportional to gamma ray energy. Then we need ...
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63 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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493 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 ...
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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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Function to fit solar radiation data

I have ground-level radiation data of solar incoming radiation from a radiometer (cosine collector) measured along the day. In the following plot you can see PAR irradiance (ie visible light) in Watts ...
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What is a photopeak?

I'm currently studying for an exam, where I'm looking into decays and gamma radiation. I then have a diagram where there are stuff like "Compton scattering", "Single Escape Peaks", "Double Escape ...
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191 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 ...
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Frequency-averaged (gray) radiative transfer

The equation for radiative transfer is $$ \omega \cdot \nabla I = \kappa(B - I) $$ where $I$ is the intensity of radiation, $\omega$ is the ray direction, $\kappa$ the absorption coefficient, $B$ the ...
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How does gamma ray emission make an atom more stable? [duplicate]

One of the types of radioactive emissions is gamma emission. I understand how the other two types, alpha and beta, help to make the atom more stable. How exactly does gamma emission help to make the ...
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124 views

What determines the distribution of the energy between the beta-particle and the neutrino in beta decay?

When beta-decay occurs an electron or a positron is emitted along a neutrino or an antineutrino. The energy spectrum of the beta particles is continuous because, as I read, the energy is shared ...
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Question on Radiance equation

The radiance equation is $$ L = \frac{d}{dA} \frac{2(\phi)}{dW cos(\theta)} (watt/srm^2) $$ where $\phi$ is the flux. I am thinking, should not be the cosine term on the numerator instead of the ...
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Per unit of energy, what radiation is the most penetrating?

This question about nuclear reactor shielding got me wondering, what forms of radiation are the hardest to shield? I suppose Neutrinos will have to be excluded since they're the obvious winner. So ...
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Can I excite an already unstable element for accelerated decay?

Say I had an unstable element ready to go through beta decay and I introduced it to high speed electrons: would this lessen the time needed for the product to go through beta decay?
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How to calculate gamma radiation shielding?

A device emits 0.2 ╬╝Sv/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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Equivalent Dose absorption from Na22 source

No idea what exactly the rules are or how I should ask this question, but here's the verbatim quesiton: "A Na$^{22}$ source has an activity of 100 $ \mu $C. If you handle the source, how big is the ...
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84 views

Radiation emission and absorption

Any object can emit and absorb radiation and the power of emission can be represented by the Stefan-Boltzmann law: $$P=A\epsilon\sigma T^4$$ In many texts the net power radiated is the difference ...
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Absorption coefficient from HITEMP or HITRAN [closed]

How to calculate the absorption coefficient (for radiation) from HITEMP or HITRAN databases? Or where can I find some tables or plots for the absorption coefficient?
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Would being underwater help survive a nuclear bomb?

If I jump in my pool, on the river near my house knowing that a nuclear bomb, or atomic or H-Bomb exploded around 10 km from my house, would I survive? The way I see it is that water will protect me ...
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“Single-shot” Heat engine efficiency limits

The sun is 5778K and Earth is ~290K. Using the sun as the hot reservoir and earth as a cold reservoir we get 95% Carnot efficiency. However, the solar power efficiency limit is only 86%, see: ...