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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Can electrons within a positive ion absorb and reflect light?

I understand that in a crystalline metallic structure, such as one making up a bar of gold, there are one, or more, valance electrons of each atom that have left their outer shell (became free ...
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Why is the intensity of an alpha ray constant along a material?

I'm taking a course in radiation physics and I've come across the following problem: A thin beam of alpha particles of intensity $I_0$ and energy $E_0$ impacts in a material. What is the intensity ...
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How many photons are there in free space on average

Estimates of the amount of for example "dark matter" are of interest to the cosmologists. However, I have never seen an estimate of how many "free" photons could be speeding about in the known ...
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Fermi's theory of beta decay - Does Fermi's Hamiltonian have the wrong transformation properties?

I'm studying the theory of beta decays as proposed by Fermi in the 30's, and I found an inconsistency between the transformation properties that he claims for his Hamiltonian and the transformation ...
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Cesium-137 From Fukushima Meltdown

I've been reading up on the Fukushima nuclear meltdown and its effects it had on the environment. The iodine-131 initially released from the incident decayed after 8 days, but other isotopes such as ...
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Are the leptons in $\beta^-$ decay already present in the nucleus in some form?

In beta minus decay, beta-minus particle and anti-neutrino are ejected, leaving behind daughter nucleus. $\beta^-$ and anti-neutrino both are leptons. Were the leptons already present in the ...
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Long distance radiation detection, David Hahn and the clock

The strange character David Hahn, obsessed with creating a nuclear reactor since a young age, was reportedly wandering around his neighborhood with a Geiger counter and by this means he located a ...
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Have cosmic rays and the CMB affected Earth's history?

Do cosmic rays and the cosmic microwave background carry with them enough energy to have a macroscopic effect on events on Earth? The most obvious example I can think of is by giving animals cancer. ...
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Does an atom become positively charged as a result of Beta decay? [duplicate]

Since a neutron breaks down into an electron and a proton, and the electron is emitted as beta particles, the atom has an extra proton (protons>electrons). So, the atom becomes positively charged. But ...
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Can neutrinos cause $^{14}\rm C\to\,^{14} N$ beta-decay?

I half-heard in a lecture that radiocarbon beta-decay is caused by neutrinos passing close to the nuclei & weakly interacting with one of the carbon neutrons, flipping it to a proton and producing ...
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How deep would a moonbase have to be dug for radiation protection?

The atmosphere of the earth protects us from cosmic rays and other kinds of space radiation. On the moon there is little to no atmosphere so anyone on the surface of the moon is directly exposed to ...
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Electron energy from beta decay

I read in my IB-physics book that the average energy for an electron in the beta decay of Potassium-40 is 0.44 MeV. However this would imply the electron have a velocity of 3.9E8 m/s, i.e. faster than ...
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Can we have Bremsstrahlung emission of particles which are heavier than the initial radiating particle?

Lets consider a light particle in a high-energy process. Can this light particle radiate "Bremsstrahlung particles" which are heavier than the initial light particle? In this context I don't refer ...
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What is the meaning of the magnitudes on the axes of this spectrum?

I'm taking a course on radiation physics and I've been given an spectrum by my professor (concretely it is a spectrum of $\left.^{22} Na \right.$). This is the first time that I come across this kind ...
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Other methods of X-ray production

Long running debate, I would like to find a definitive answer. In a long glass tube (borosilicate or other common glass) with high frequency AC excitation at one end, 50-60kV, with high evacuation, I ...
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Direction of the radiation reaction force (vs. velocity)

The radiation reaction force is proportional to $\dot{\mathbf{a}}$, and can be derived from the the Larmor power using the concept of the conservation of energy. Looks like the radiation reaction ...
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Question about Cavendish experiment

I got a question. In Cavendish experiment was used lead in both of spheres. Can we repeat that experiment with balls made from stone or anything else. Because lead could be a byproduct of radioactive ...
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Meaning of mean free path expressed as kg/m^2?

In the paper "The Question of Pure Fusion Explosions under the CTBT" at reference 12, the equation for the neutron dose from the fusion of a small amount of DT gas is given, with a term of $90 ...
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Could the $\gamma$ ray “weaken law” be used in the air?

I'd better write it down. I do not know if it is called "weaken law" in English. $$N=N_0e^{-\mu d}$$ $N$ is the initial number of photons. $N_0$ is the amount measured after passing through an ...
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Do all thermal radiators have the same surface brightness?

Imagine I heat a piece of metal to 1000K. It will be red hot and will emit black body radiation corresponding to this temperature. But what about the brightness? Assuming the bulk is opaque, does it ...
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Hot Object In a Cooler Space [closed]

How would you calculate the heat given by an object that is hotter than its surroundings? I know there's Newton's Cooling Law, but what about any heat given off by radiation? Are these additive ...
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Radiation weighting factor photons

I'm wondering about the equivalent dose and the radiation weighting factor of photons (according to ICRP 103). Why is the weighting factor independent from the energy of the photons?
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How do molecules absorb heat?

How do molecules absorb and retain heat, and how is that heat able to still affect nearby molecules? On Venus there is a green-house effect where the large, dense Carbon-Dioxide atmosphere absorbs ...
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How can I estimate the number of X-Ray photons generated from a x ray tube?

I have this problem. I have an x ray tube of which I know the specific (kV, mA, anode material) and I have to estimate the number of X ray photons hitting the sensor after passing through air and ...
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Radiation by an accelerated charge

An elastically bound electron vibrates in simple harmonic motion at frequency $\omega$ with amplitude $A\;.$ Find the average rate of loss of energy by radiation. So I think I can use ...
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Understanding Vaidya metric and pure radiation stress-energy tensor

I am following Vaidya metric and how it is related to pure radiation from Wikipedia. But when it reaches the line where stress-energy tensor is equated to product of two four-vectors, I cannot follow ...
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How does a gas emit radiation with temperature when it's particles motion are linear?

Particles in gas move faster with temperature in a linear motion (root mean velocity equation?) right? It explains increase in pressure and effusion proportional to temperature. Solids emit radiation ...
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Effect of radiation pressure on Earths orbit in large timescales

I have seen some posts concerning the radiation pressure exerted by the Sun on Earths surface (Force on Earth due to Sun's radiation pressure). Though it is fairly small may it have a considerable ...
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What is the difference between beta positive decay and proton decay?

Though beta positive decay's have been observed, in which a proton decays into a neutron, positron and an electron- neutrino; the why is it not the same as the exotic proton decay which is ...
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How does mass affect the range of a nuclear particle?

Heavy particles such as protons and alpha particles of certain energy will lose all their energies in a definite distance in a medium, and this distance is called the range. The range is the distance ...
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Relativistic explanation of Radiation

I ask this question again in a simpler, shorter form. Maxwell's equations can be derived with Special relativity starting from the Coulomb's law. Therefore all the phenomena of classical ...
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Radiation heat loss and reuse

When the human body lose radiation heat rays, is there a way we can pick it up and collect it? And then use it over again by fex. using a heat exchanger and a device that can emit them (rays) back out ...
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Light interference with light and other EM waves [duplicate]

Lets assume a room with one or two sources of light (normal light bulbs or fluorescent lamps). So if we look at lamp from any direction we see it. We also see different objects in the room because of ...
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Is there a gravitational radiation reaction force?

As you may know, the linearized relativity theory (or gravitoelectromagnetism), obeys equations analogous to Maxwell's equations in electrodynamics. These equations in ED result in the troubling ...
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Can alpha, beta or gamma radiations emitted by a radioactive substance be controlled? [duplicate]

Just saw this question in a school class 10 exam. Google search did not yield useful results. Can anyone please explain the answer here?
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How Much Does Roof Color Affect Energy Consumption?

I'm not sure whether this is off-topic; if so, I do apologize and will fully understand votes to close. That said: I live in a climate that's quite cold much of the year but gets pretty hot in the ...
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Beta decay - Relative probability of electronic conversion for different disexcitations energies

I'm studying, experimentally, beta decay phenomena. Internal conversion of electrons happens when we have a sobreposition between a excited nucleus with it's electronic cloud. The colision between the ...
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Does adding static charge to a body increase its mass?

If a body becomes charged by losing electrons for example, it will experience a braking force when it is accelerated due to radiation called Bremsstrahlung radiation. Part of the energy used to ...
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how is the state parameter determined?

For radiation, dark energy and dust the pressure and energy density are related, respectively, by: $p=\frac{1}{3}\rho$ $p=-\rho$ $p=0$ My question is why? How does one show that this is how ...
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Confusion about radioactivity

The following question is from General Problems on Physics by I.E Irodov 6.220. Find the decay constant and the mean lifetime of $^{55}\operatorname{Co}$ radionuclide if its activity is known to ...
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Smart capsules for radioactive metals

If we add or remove an election to the atoms of radioactive metals, they will become the isotopes of their adjacent chemical elements in the periodic table. I ask the community whether the resulted ...
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Measuring Activity

The formula for Activity of a radioactive substance is $ \frac{dN}{dt}=A=λN $. If we have an initial number $N(0)$ of some Radionuclide, which has a halflife of, say, 12 hours, is there any ...
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Modeling total absorption using absorbance of multiple visual layers

I have a question involving light absorbance versus absorption. It applies to a stack of different photoreceptor types. I understand the difference between absorbance, which is basically equal to ...
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Question on decay constant

I have a model of the radioactivity of a target which is undergoing Neutron Spallation. The Protons are incident upon the target for approximately 200 hours. Within the model, over the course of ...
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Is (or why isn't) static charge as lethal as ionizing radiation?

Ionizing radiation, e.g. the "stuff" emitted by radioactive materials, is dangerous to humans since changes to the electron configurations (in the human body) causes the various molecules (in the ...
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Can a single particle be “heated” by radiation?

From the point of view of statistical thermodynamics, a single particle doesn't have a phase (state of matter), nor temperature. What would happen if heat is transported to this single particle via ...
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Determination of radiation pressure

Consider the incidence of an electromagnetic wave on the plane $x=0$. We have that: $$f_x=\frac{dF}{dV}$$ $f_x$ is the volumic force density on the medium. My doubt is purely mathematical. I ...
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Is the direction of gamma-ray emission by a nucleus totally random?

Let's consider an excited nucleus emitting one gamma-ray (not cascade etc). Is the direction of gamma-ray emission completely random? In other words, is the probability to detect this gamma equal for ...
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If UV radiation 1 cm away from the halogen bulb is equal to Sun's radiation, what is the level of radiation 1 meter away?

Halogen light bulbs emit some amount of UV radiation, and some sources consider them dangerous. Here it is written, that UV radiation (of certain types) from a particular halogen bulb was equal to the ...
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How can a string vibrating in a plane radiate sound?

If a plucked guitar string vibrates in a plane, how are waves produced that travel in all directions? I'd have thought that a vibrating string can only produce waves in its plane of motion.