Questions tagged [radiation]

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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What is the input of calculating signal noise ratio (SNR) and detective quantum efficiency (DQE) in estimation of imaging system?

In its definition, the signal noise ratio (SNR) is the ratio of the mean siganl to the standard deviation of the noise. However, for a given picture what is the noise? The detective quantum efficiency ...
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How dangerous would it be to sleep in a bedroom with 1,000 vintage clocks? [closed]

Imagine a fairly small bedroom with shelves lining all the walls. The shelves contain 1,000 vintage clocks. Some number of them - say 80% as a guess - have dials that were painted with radium. In the ...
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Do supernovas vaporize the local space rocks 10 Pluto distances away?

In a follow-up to this question, What would it be like to watch an average space rock / ice comet at 1-20 Pluto distances from a supernova of $10^{44}$ joules? At what proximity would they become ...
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How does apparent brightness (or stellar magnitude) change with distance in an expanding universe

Cosmological redshift causes wavelengths of a distant object to stretch by a factor $1/(1-Hr/c)$ where H is the Hubble constant, r is distance, and c is the speed of light. Consequently the received ...
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Why can $d E$ be represented as $ I_\nu \vec{k} \cdot \vec{n} dA d\Omega d \nu dt$ in radiation?

The appropriate definition of specific intensity can be something as following: Construct an area $dA$ with the normal direction of $\vec{n}$, and the direction of the ray is $\vec{k}$. Consider all ...
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Is the energy of a Bremsstrahlung photon proportional to radiation from the Larmor power?

Wikipedia gives the total radiated power from Bremsstrahlung by the Larmor formula, and then compares the results for electrons and protons. It states that due to the mass difference and $\gamma^4$ ...
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Is it possible to calculate ion species fractions from relative intensity optical spectra?

I'm trying to find references or instruction on how to calculate or at least estimate the ion population or population fraction from the optical spectra of a plasma. I have found tables that provide ...
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Derivation of the planet flux observed at Earth (solid angle problem)

I'm having issues understanding how Sara Seager, in her book "exoplanet atmospheres", determined the solid angle subjected to a detector on Earth. By the figure: The solid angle was defined ...
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Aligning 4 Plane Lasers to a single point for Radiation Isocenter

I am interested in aligning 4 lasers. The lasers are positioned in a square room two across from each other and two on the ceiling pointing down. Each laser projects a y and x planar beam. I would ...
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Is there impedance when there is nothing else?

With the exception of gravitational waves, all the information about the universe we gained from electro magnetic waves which we agree to run at the speed of light for all the spectrum from far ...
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Why we have not observed one proton and one neutron nuclear decay? [duplicate]

I'm learning about nuclear decays: Alpha (helium nucleus, +2) Beta (electron) Gamma (photon) Neutron But why helium nucleus? Why not hydrogen nucleus (deuterium)? I mean why two protons and two ...
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Calculate total number of fluence on a moving detector

We have a radiation zone emanating from a source located at $(x_0, y_0, z_0)$. We also happen to have the flux due to this source measured in a 3d cylindrical grid surrounding the source with a flux, $...
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How do physicists know that some of a beta ray/particle's 'missing' energy isn't lost to interference with the electron cloud surrounding the atom?

Enrico Fermi and Wolfgang Pauli ultimately concluded that beta decay resulted in an electron and an electron antineutrino leaving a nucleus... BUT... How does the electron leaving a neutron punch its ...
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Why is beta minus particle denoted to have -1 proton number?

Why is beta minus particle denoted as having -1 as proton number?
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Diffrence between thermionic emission and photoelectric emission

Thermionic emission involves heat energy to excite the electron and remove it. In the photoelectric effect, a beam of light is involved. As per my understanding heat and photons, both are energy. Heat ...
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Find the maximum possible energy for a beta-particle decay-chain [closed]

So I have this problem where I'm supposed to find the maximum possible energy for a $\beta$-particle in the following decay-chain: The first decay: $$^{90}Sr\rightarrow ^{90}Y + \beta^- + \bar{v}_e$$ ...
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Is diamond a good neutron moderator?

The title mostly says it: Is diamond as a material a good neutron moderator for nuclear fission reactors? Or: Could you build a nuclear fission reactor with diamond as a moderator, instead of graphite....
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Radiation pressure at a oblique surface

I am doing a problem that asks the radiation pressure of a beam of light on a oblique surface. The problem says: A laser beam of intensity I reflects from a flat, totally reflecting surface of area A, ...
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Why is radioactive half-life constant?

Say you have just four radioactive atoms with a half-life of one hour. (I am using a small number of atoms to keep it simple and illustrate my confusion more clearly). So that means one hour from now, ...
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How does gamma radiation ionise atoms?

I am having trouble understanding how gamma radiation can ionise atoms. I think it is due to a lack of understanding about how photons work. My basic understanding is that gamma radiation doesn't ...
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Intensity of Compton scattering photons

In various sources (1, 2, 3, 4, to name a few) I have seen this graph shown below, that shows how intensity depends on the wavelength of the scattered photon $\lambda'$. Now, I do understand what ...
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What range of light on the electromagnetic spectrum are produced by the de-excitation of electrons?

When an electron moves from an excited state to its ground state, a photon is emitted, which is the source of light. However, I know that the highest energy form of light, gamma rays, are produced ...
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How to estimate the power produced by this small U-238 check source?

I got this sealed check source to test my pancake detector (tube model is LND 7317). But I'm wondering if it's worth trying to collect some of the tiny amount of power it's producing as a fun home ...
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Is Terahertz SAR imaging of Earth possible?

The Terahertz band is at the Wavelength range of 1 mm to 100 μm, which is very good for synthetic aperture radar aka SAR since the shorter the wavelength the better angular resolution you get. ...
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Why do electrons come to ground state even after giving absorbing energy?

Imagine you have a hydrogen placed under sunlight, now if we look at 1st shell of hydrogen, it has energy of $-13.6$ev now for 2nd shell we have energy of $-3.4$ev. 1st shell -> $-13.6$ev 2st ...
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Density problem [closed]

Spacecraft are commonly clad with aluminum to provide shielding from radiation. Adequate shielding requires that the cladding provide 20. g of aluminum per square centimeter. How thick must the ...
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Spacelike geodesics of FLRW radiation universe

I'm having an interpretation problem with the radial spacelike geodesics in the flat radiation dominated universe. I'm using standard conformal coordinates $\eta \ge 0$ and $\chi \ge 0$ for the ...
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Alpha decay of 202-Rn

We were given the following decay scheme of 202-Radon in the 0+ state, with Q-value 6.7737 MeV Spin-parity Energy above ground state (keV) E_a I_a $0_2$+ 816 5836 0.0018 $2+$ 604.94 / / $0_1+$ 0 ...
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Does the absorption of ionizing radiation increase the absorber temperature?

Let's say a gamma ray shielding material (assume water) has absorbed 1 joule of gamma ray ionizing radiation, does the absorbed 1 joule eventually end up as heat in this material? I ask this question ...
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Hawking radiation question

A stationary observer near the black hole horizon will detect Hawking radiation proportional to their local acceleration. If we call $\alpha=\frac{GM}{r^{2}}\frac{1}{\sqrt{1-\frac{2GM}{r}}}$ the ...
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How can I perform particle identification with a proportional counter? I mean, how am I able to discriminate between an alpha particle or beta rad?

As far as I understood for PID you need to know the momentum, the charge and the energy loss by the particle. So if I measure a certain energy loss with a proportional counter how can I know that I ...
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Why $\rm Ag$ 108 decays into $\rm Cd$ 108 most of the time?

In the table of nuclides, it shows that $\rm Ag$ 108 can go through either electron capture or beta- decay (though the branching ratio for electron capture decay is much lower). What determines that? ...
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Acceleration due to incident radiation on plate

I have tried the following question and getting a wrong answer. Monochromatic light of intensity I falls over a blackened plate of area A, at an angle $\theta$ as shown in the figure. If 70% of light ...
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How can negative beta-decay energy be negative?

The International Atomic Energy Authority (IAEA)'s Nuclear Data Services list tables of nuclear data, including a table of atomic masses and beta decay energies, data taken from Huang et al., Chin ...
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What would be the theoretical energy required to make a "microscopic" temporary black hole that could move an atom?

I stumbled across some videos/news about The Large Hadron Collider and all the panic around the possibility of it creating a black hole. Of course, it is impossible to create a black hole and from all ...
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Electrons in Atom in different energy states

I have a very basic doubt in Bohr's Atomic Model. I just studied that an electron can go to any Energy State with in the atom, by getting relevant energy from photons. If an electron goes to 2nd ...
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Will a radioactive ball conserve its angular velocity?

Consider a uniform spinning sphere in vacuum. In principle it should spin forever, because of angular momentum conservation. However, assume that the sphere is made of radioactive material: since it ...
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Cavity and black body radiation

If one speaks of the fact that one gets blackbody radiation in good approximation by a cavity with hole, does one mean as blackbody this hole, i.e. the place where the radiation exits from the cavity? ...
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What are some household sources of radiation detectable with a geiger counter?

I recently started rock tumbling with my preschool-age kids and bought a cheap geiger counter to check out rocks we find (more from curiosity than concern). Specifically it's a GQ GMC-500Plus model ...
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Why aren't electrons accounted for when calculating the energy of nuclear decay? [duplicate]

In my physics exercises, I had to calculate the energy generated by the decay of an atom of the isotope 40 of K by Beta - decay. It gives us the products: isotope 40 of Calcium and one electron. When ...
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How can beta decay change elementary particles?

From what I read on beta minus decay, when it happens a neutron gets "converted" into a proton, an electron and an electron-antineutrino. I also read that both the neutron and the proton are ...
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Unexpected distingration energy value during alpha decay equation [closed]

I am trying to solve the disintgration value of the below decay equation but the issue I am having is my result seems way to high compared to what is expected (around 5-6 MeV). $$^{213}At \rightarrow ...
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Can point masses following geodesics and orbiting one another emit gravitational radiation?

I am a bit confused about this situation: according to general relativity, when two masses orbit one another, they emit graviational waves, which carry away certain energy. For example, check out ...
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Do unstable nuclei affect each other for decaying?

I am thinking about beta decay. If we graph decayed nuclei count over time, we don't see a linear line. Rather, it would be a curved line. I imagine myself as an unstable nucleus. If I don't care ...
5 votes
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Does thorium-232 emit X-rays?

The question is derived from an experiment... "Red" tungsten TIG welding electrodes consists 2% of thorium-232. They are slightly radioactive... I have such electrodes, so I checked their ...
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How was the black body intensity vs wavelength (or frequency) radiation curve historically produced?

I have read that Wilhelm Wien gave his formula to match the radiation curve of a black body as shown in the picture; which works well in high frequency region. Another formula by Rayleigh-Jeans is ...
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Black body side of the Moon

A few closely related questions regrading the Moon thermodynamics: The Moon is clearly not a black body, as it reflects a great deal of radiation incident on it. Still, it does absorb some radiation ...
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Has there been experimental confirmation of electron capture being a neutrino source?

Detecting nuetrinos is not easy of course but it seems that there are several interesting ways of playing with neutrinos using radioactive sources that can only decay by electron capture. For example, ...
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How does air cool as it nears the poles?

I understand air is heated by the equator causing it to rise towards the poles. But why does air cool and sink after nearing the poles. Shouldn't the air still possess heat, after being heated by the ...
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How long does it take, and how much heat, to raise the temperature of air in a box?

I am seeking to crudely model a house with a window as a perfectly insulated box with a hole (which only allows radiative heat). My question is to find how the temperature of air in the box changes ...

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