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 does heat travel?

How does heat travel? I have two competing thoughts here!! Firstly some form of atomic/molecular process liberates a photon in the infrared region of the spectrum which is detected as heat by a ...
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104 views

Cobalt 60 beta decay

In the beta decay of an atom of Co60, the radiation you would expect is one or two gamma rays, plus an electron plus an electron neutrino (and in the nucleus Ni60+, if I understand it well). However, ...
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35 views

Explanation of binding energy in decays

Everyone knows that the mass of a system is less than the mass of its components, with the equation: $M = \sum_i m_i - BE(M) $ Now, if we consider a general decay, lets say $A \rightarrow \sum_i ...
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What causes different decays?

Nuclei spontaneously decay according to a certain decay rate. There are however different kinds of decay, alpha, beta, gamma... What causes then the nuclei, when they decay, to do so in one way of ...
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94 views

Is it possible to calculate the half-life of a nucleus?

Is it possible to calculate theoretically the half life of a nucleus (how?) or they are all known through measurements? As an example how do you calculate the half life of Carbon-14?
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57 views

Proof of the inverse square law for a uniformly bright sphere

On page 8 of "Radiative processes in Astrophysics" by Rybicki and Lightman they have a proof that the flux of a uniform sphere is inversely proportional to the distance of the sphere from the ...
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286 views

Conservation of mass-energy and nuclear transmutation

This may just be beyond the grasp of the everyman, but I'm trying, and failing, to grasp how conservation of mass-energy works in cases of beta decay and electron capture. A neutron has a mass of one ...
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2k views

A hot object exposed to low temperature in a vacuum doesn't lose heat?

I heard somewhere that if the human body were exposed to outer space where the temperature is extremely low, the human won't actually feel cold because in a vacuum, the heat energy doesn't have ...
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283 views

$\alpha$ and $\beta$-decay, why don't they neutralize each other?

$\alpha$ radiation consist of positive charged helium nuclei, $\beta$ radiation of negative charged electrons. So why don't the $\alpha$ particles take those electrons to get neutral?
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42 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 ...
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346 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) ...
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26 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 ...
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98 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 ...
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102 views

How damaging is light? [closed]

On Surely You're Joking Mr Feynman, when talking about the Trinity test, the author states: the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet ...
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81 views

X-ray production rate [closed]

A 100 MeV proton beam of $10^{14}$ proton/s is perpendicularly incident on a rhodium foil 25 $\mu$m in thickness. Estimate the production rate of K and L x-rays(use the figure below). So far I ...
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109 views

Physics and Skin Color: What differences do physicists observe between different skin colors?

I majored in social sciences, so I haven't taken a science class since 1999, so forgive me if I don't ask this right. What difference would skin color make from a physics perspective? Would there be ...
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How to measure the wavelengths of ultraviolet lines in the hydrogen spectrum?

how to measure the wavelengths of ultraviolet radiation isn't it invisible? it's possible to measure visible radiation but how to measure invisible radiation?
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Kirchhoff law of thermal radiation

Kirchhoff's law of thermal radiation states that for thermal equilibrium for a particular surface the monochromatic emissivity $\epsilon_{\lambda}$ equals the monochromatic absorptivity ...
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117 views

What type of Radiation hits Europa

I was recently reading the Wikipedia Page for Europa as I am interested in terra-formation. In one of the sentences, it says that: The radiation level at the surface of Europa is equivalent to a ...
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90 views

Nuclear transition notation

I have a question which asks me to determine what x is for the following nuclear transition $$^{29}Si(\alpha, n)X$$ But I don't have any idea what this notation implies. Another example: ...
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230 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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69 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 ...
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29 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 ...
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43 views

Calculate transparency from Beer-Lambert Law

I want to calculate a transparency parameter for a superposition of several volumes containing media using the Beer-Lambert Law, which states that $$I/I_0=exp(-\tau)$$ where $I$ is the transmitted ...
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1k views

Absorption cross section and absorption coefficient

What is the absorption cross section, how is it measured? How to convert it to the absorption coefficient (measured in cm$^{-1}$)?
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70 views

Is it possible to generate electric energy from the radiation of radioactive materials

I wonder if it is possible to generate electric energy from the radiation of radioactive materials like nuclear waste? If it is then wouldn't that also mean that it could be used as an energy source ...
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internal conversion and the electromagnetic force

I have read that the mechanism behind internal conversion, in which a nuclear transition leads to the ejection of an electron in one of the lower atomic orbitals, is related to the fact that the ...
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90 views

Blackbody radiation and Spectral Lines [duplicate]

Blackbody radiation is thermal radiation from a hot object emitted over a continuous range of wavelengths. But why are spectral lines, lines (i.e., you only get certain wavelengths when an element is ...
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79 views

Use of fission products for electricity generation

Why can't we use fissions products for electricity production ? As far has I know fissions products from current nuclear power plants create enough 'waste' heat to boil water; and temperature ...
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75 views

interior surface of furnaces

For industrial furnaces, in order to improve radiation heat transfer and save energy, some people say applying a high emissivity coating on to the interior surface of a furnace will do, while some ...
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192 views

Does blackbody radiation work like this?

In a blackbody object the photons are reflected back and forward. If I heat up the the blackbody object with microwaves or other types of photons the electrons in the wall would vibrate. When the ...
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Is terahertz radiation new?

Regarding the future applications of terahertz technology, I thought we already knew the entire electromagnetic spectrum. In fact we do not, terahertz lies between microwaves and infrared radiation. ...
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122 views

Absorption of radiation due to temperature

I was wondering if the temperature of an object affects the amount of radiation it absorbs. For example, if I have a box that is hotter, will it absorb more energy as compared to the same cooler box? ...
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59 views

Definition of isotropy of radiation and its consequences

I have encountered different notions of isotropy of radiation and I would like to know if they are the same and what the exact definition of isotropy is, if one exists. Let's take black body ...
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425 views

Is compton scattering only effective by x rayphotons and gamma ray photons

Can Compton scattering work with any other forms types of photons, and why was the the Compton Scattering experiment only done with x ray photons?
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281 views

How is the energy distributed in a proton-antiprotion annihilation?

I know the products of the annihilation, but I don't know how much energy each particle has or gets. For example I know that 1876 MeV is released for each annihilation. Now, this energy is distributed ...
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190 views

Reflection, transmission, absorption…how to calculate them?

I was wondering whether there is an equation that enables me to calculate the reflection, transmission, absorption and polarization, when the electric field everywhere is given? Consider this: You ...
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33 views

The Observance of Electromagnetic Phenomena

As far as I've seen, E&M waves are sinusoidal. Our eyes observe these patterns and give us colors, but in a situation like such: Why do electrons emit radiation? There is still a wave, or at least ...
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When should angles be expressed in degrees vs. radians?

I am trying to calculate the albedo of a given latitude by following the methods of Brutsaert (1982), I have copied the formula below: 3.6 Shortwave and long-wave radiative fluxes Albedo ...
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What was the first ionization radiation?

While trying to make somewhat of a timeline of the history of ionizatig radiation, i am wondering about the following questions: The first photoelectrical effect was found 1839 by Alexandre ...
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109 views

Quantum yield and spontaneous decay

I'm trying to figure out how many atoms are decaying spontaneously in a span of 2 seconds. Let's say that the quantum yield is 0.45, and that the lifetime "τ" (tau) is 10 microseconds. Then I found ...
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294 views

Specific electron energy gap values $E_{i+1}-E_i$ vs. photons with arbitrary energy $\hbar \omega$

The energy levels of electrons in an atom are quantized $E_i$. A photon of a specific momentum $\vec p$ and energy $$\omega=(E_{i+1}-E_i)/\hbar$$ hits an atom and gets absorbed. Okay now say the ...
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213 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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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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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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61 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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646 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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51 views

how hot is Plutonium-238 in 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 ...
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26 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 ...
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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?