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.

learn more… | top users | synonyms (2)

1
vote
1answer
23 views

Does the W boson in beta decay affect the gravity generated by the system?

During beta decay we now know a heavy W boson gets involved temporarily. Would this potentially impact the gravitational field generated by the system as a whole? It doesn't seem like it should. Just ...
0
votes
1answer
61 views

Relationship between temperature and wavelength?

I am investigating the relationship between wavelength and temperature. As seen the figure below of Planks law What is the relationship between the lambda(max) and Temperature? or in simpler ...
0
votes
0answers
16 views

beta minus decay: expression for maximum electron energy

I'm having some trouble finding an expression for the maximum electron energy in beta minus decay. In the frame where the neutron is initially at rest, conservation of momentum reads: ...
0
votes
1answer
34 views

X-ray background radiation

I'm running an experiment in gamma-ray imaging (although the main emission from the decay of Am-241 is ~60keV, so much more in the range of x-rays). I'm curious as to the sort of sources that would ...
0
votes
1answer
21 views

Background gamma radiation

There are plenty of lists of sources of general background radiation, but can anyone reduce that list to the major contributing sources purely for background gamma radiation (specifically low energy, ...
1
vote
1answer
32 views

What process happens in an IT nuclear decay?

I've been researching medical isotopes and alot of them decay by an IT path. Does anyone know what IT stands for? And what physical process is happening? Example: ...
2
votes
2answers
94 views

Why the CMB has not been dispersed so far?

Imagine you have a box of black body radiation. What happens if you open the box for a long time? It becomes dispersed and no radiation remains in the box. Now, apply this example to the Cosmic ...
1
vote
2answers
144 views

Why do microwave ovens use radiation with such long wavelength?

According to Wikipedia: Consumer ovens usually use 2.45 gigahertz (GHz)—a wavelength of 12.2 centimetres (4.80 in). Typically, I put the dish inside the oven in its center. I suspect most ...
1
vote
2answers
37 views

Lethal dose of Gy's (Grays)

The unit Gray has the dimensions $\text{J/kg}$. I've read, that a dose of about 3-5 Gy's could kill a person within a few weeks - or at least that's usually the case. But I'm not really understanding ...
2
votes
0answers
39 views

How do experimental physicists know the decay path of transuranium elements ahead of time?

I have been watching (and enjoying) Dr. Poliakoff's YouTube videos on the synthesis of transuranium elements like Roentgenium and Copernicium, which decay so quickly that they are identified (if I ...
0
votes
2answers
24 views

Radiometric dating calculation [closed]

If a sample of zircon initially contains no Lead, find an expression for the ratio $$\frac{N_U}{N_{Pb}}$$ as a function of time? How do I do simplifications from this? Do I just go: ...
0
votes
2answers
29 views

Is the screen in CRT connected with a positive pole?

I don't understand this passage would you clarify it? "These electrons are then freed (liberated) from the metal and are then picked up by the screen, which is connected to a positive pole called the ...
1
vote
1answer
43 views

Working out the penetration of radioactive decay products

From my understanding of the products of radioactive decay (alpha particles, beta particles, and gamma are all I know of), the particles (or energy I guess?) are stopped by a medium according to it's ...
0
votes
0answers
27 views

Continuum Wave Function for the electron

I'm trying to understand certain processes like the photoelectric effect and Bremsstrahlung. In Bremsstrahlung I need to use the wave function of an electron coming from the continuum, and there is ...
0
votes
1answer
24 views

Spin and parity transition levels gamma radiation

Just a quick question regarding spin and parity. I am studying nuclear physics and I am just a tad confused with a concept about gamma radiation. Say I have ${^{20}_{10}Ne}$ And the lowest electric ...
0
votes
0answers
28 views

thresholds for Cherenkov radiation visible to the human eye

In pool-type fission reactors, the beautiful Cherenkov radiation from the beta decay of intermediate products seems to be a well-understood phenomenon. I am wondering what some ballpark figures are ...
0
votes
2answers
38 views

Where does the “Illumination Formula” come from?

I've been studying for the pGRE for the past couple of weeks (what a load of... nevermind), and one of the questions requires the use of what is apparently deemed the illumination formula, used to ...
0
votes
0answers
44 views

Why does a damped quantum harmonic oscillator have the same decay rate as the equivalent classical system?

$\newcommand{ket}[1]{|#1\rangle} \newcommand{bbraket}[3]{\langle #1 | #2 | #3 \rangle}$ Why does the decay rate for a damped quantum harmonic oscillator exactly match the classical limit? Background ...
2
votes
3answers
96 views

Why do neutrons decay after 6 minutes?

If I understand correctly, Beta decay only occurs when an atom (or in this case subatomic particle) is unstable. Are neutrons consider unstable? If so why? And if they are not unstable is there is ...
2
votes
1answer
54 views

Would the blue glow of Cherenkov radiation be visible when diffused across ice, such as in the IceCube neutrino experiment?

The blue glow characteristic of Cherenkov radiation is visible emanating from underwater reactors. Is it also visible through ice, at the IceCube neutrino experiment (not that anyone is physically ...
0
votes
1answer
50 views

Emissivity of vacuum for radiation heat

What is the heat radiation emissivity of vacuum? For air as well? What is the difference? I understand that the vacuum has reflectivity of 0, So what is the other two values are in $$ reflectivity + ...
2
votes
1answer
72 views

How would the explosion from a Pure Fusion Bomb differ from the explosion from a Fission Nuclear Bomb?

Suppose we have the technology to create high enough temperatures and pressures inside a confined space to fuse together deuterium and tritium, and create a Pure Fusion Bomb. How would the explosion ...
1
vote
1answer
85 views

How hot is Plutonium-238 in Radioisotope Thermoelectric Generators (RTGs)?

As I understand it, Plutonium-238 is used to provide power through heat generation in radioisotope thermoelectric generators. My question is... how hot is a pellet of Plutonium-238? Does the heat ...
1
vote
1answer
85 views

Does tin foil keep heat out?

For example, if i were mailing a box of chocolates and lined the inside of the box with foil, then wrapped the chocolate in bubble wrap and placed it inside the foil lined box, would the box heat up ...
2
votes
1answer
41 views

pGRE question on natural line width

The lifetime for the $2p \rightarrow 1s$ transition in hydrogen is $1.6 \times 10^{-9}$ s. The natural line width for the radiation emitted during the transition is approximately... Their solution: ...
0
votes
1answer
48 views

Reactive near field for Wireless Power Transfer (WPT)

In literature it is stated that in reactive near field using high-Q coils in resonance the efficiency does not depend on coupling (ie. distance) and that coupling only has influence on rate of energy ...
1
vote
1answer
390 views

Deriving Gamow factor for potential with effective centrifugal potential term

I am looking at deriving an expression for the Gamow factor for $\alpha$-decay. I understand that the potential is the sum of the nuclear, electric and effective potentials: $$V(r) = V_N(r)+V_c(r) ...
0
votes
0answers
24 views

What is a high brilliance X-Ray and how is one created

I just found this term being used in a Stanford Engineering year in review 2013-2014 "X-rays illuminate path to more efficient fuel cells" that cited this work. Never heard the term before and I came ...
0
votes
3answers
82 views

We don't know when a nucleus will decay. Then how can find its half life? [duplicate]

I mean how can we say that in 5730 years, 1/2 the no. of C14 nucleus will decay because in reality we don't know when a particular nucleus will decay
4
votes
1answer
154 views

What is the temperature of the clear night sky from the surface of Earth?

Before you all jump in with 2.73 K or thereabouts, this is more of an experimental question. It will obviously depend on humidity and radiation being scattered back towards the surface of the Earth. ...
1
vote
1answer
58 views

Highest background gamma ray energy?

What is the highest naturally occurring gamma ray energy that you would see in background? And what is it is source?
0
votes
1answer
52 views

Energy of resultant photons from meson decay

I am a little unsure how to answer the following question, Find the energies of two photons emitted in opposite directions along the pion's original line of motion if the pion has a r.m.e of 500MEV ...
2
votes
2answers
151 views

Solar spectrum units

Why is intensity $I$ on a graph of the solar spectrum always showed in units of $[\mathrm{W/m^2/nm}]$ instead of simply $[\mathrm{W/m^2}]$? (The y-axis on the graph.) It is apparently shown as ...
1
vote
0answers
27 views

Are the Van Allen belts important to life? [closed]

Is it significant for life on Earth? Mars doesn't have this. Why do experts think there may be life on it? What kind of life form could live on Mars? This article I just read got me wondering. A ...
0
votes
0answers
17 views

What are the principle factors that limit $\beta$ decay to elements with atomic number, Z 100 or less?

I learned for the first time in Eric Scerri's new book A Tale of 7 Elements that $\beta$ decay does not occur for elements with atomic number, Z > 100. I did some further web research on this subject ...
1
vote
0answers
24 views

Can the half-life of a free neutron be calculated or is it just empirical? [duplicate]

Everyone keeps telling me its just 10.3 minutes and no one knows how to get that number form theory. Any idea?
0
votes
0answers
19 views

Determine the number of grays absorbed by human emitted by Uranium 238

I want to count the estimated value of gamma radiation (in Grays) absorbed by human emitted by Uranium 238. Weight of it's ore is about 20 grams. The human weight is about 70 kilograms, he was about 5 ...
0
votes
3answers
99 views

Why is signal bad in a tunnel?

Consider this: you are driving through a tunnel listening to your AM radio and a GPS, all of the sudden AM radio has nothing but statics and your GPS says "reconnecting - please hold". You say to ...
1
vote
1answer
31 views

Why is 0 $\nu \beta\beta$ decay often written with electron emission and not positron?

According to http://www.cobra-experiment.org/double_beta_decay/ I can see that double $\beta$+ decay is possible, but I often find neutrinoless double beta sources with the double $\beta$- decay ...
4
votes
5answers
311 views

Confusion about Length Contraction (ex in Muon decay)

I am a bit confused about the implications of length contractions; For example, in the muon decay problem, we assume that the distance between the muon and the earth is contracted only in the frame ...
0
votes
1answer
39 views

Problems with calculating Strontium-90 leakage due to Fukushima accident

Not long ago there was a spill of radioactive water at the Fukushima plants. Here are the data: $230 \times 10^6 \,\,\mathrm{Bq}$ of beta radiation are found in a liter of water. $t_{1/2} = 28.79 ...
3
votes
2answers
101 views

Does positron-electron annihilation preserve enough info to reverse exactly

An electron-positron annihilation can produce a pair of gamma rays. In the reverse process, known as pair production, can the gamma rays carry enough information to determine the resulting ...
2
votes
4answers
135 views

What does the exponential decay constant depend on?

We know the law of radioactivity: $$N=N_0e^{-\lambda t}$$ where $\lambda$ is the exponential decay constant. My question is: This constant depends of what?
0
votes
0answers
48 views

Definition of mass gap [duplicate]

Why do we say that a system with mass gap has correlation function which decays exponentially and one without a mass gap has a slower power law decay?
1
vote
1answer
30 views

Can you heat something in AL foil using IR?

Is it possible to heat up, let's say, a blob of mud, golf ball size, covered in AL foil, with IR? Also, how efficient would that be? Is there an IR wavelength that would get absorbed far better than ...
1
vote
1answer
35 views

$\beta^+$ decay question

I read that all baryons apart from the proton itself decay into protons (why though?) and that mesons do not decay into protons due to having less mass than protons. Thus it makes sense for the ...
1
vote
1answer
123 views

Calculating the Sun's emitted power in a wavelength range?

Is there an equation that describes the Sun's emitted power on the surface [in $\frac{W}{m^2}$] over a selected wavelength range (from $\lambda_1$ to $\lambda_2$) ? I am guessing this can be ...
4
votes
1answer
1k views

What common materials absorb most infrared light?

I'm competing in a simple robotics competition where most of the participants use reflected infrared light to detect their opponent. I'd like to make my own robot as difficult to see as possible. What ...
1
vote
2answers
81 views

Earth's and Moon's outgoing radiation

Does Earth or Moon emmit/reflect anyother form of radiation than IR into space? I am especially curious if they emmit/reflect UV radiation. And if they do, where could I find an irradiance spectrum ...
0
votes
0answers
36 views

Can the half-life of rubidium 87 be theoretically estimated?

Can the Fermi golden rule be applied to give an approximation of this half-life?