Questions tagged [radioactivity]

The property of some materials by which individual atoms decay, emitting energy or particles often transforming into different elements in the process.

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What is the extreme long-term elemental composition of the universe?

In Freeman Dyson's classic 1979 Time Without End paper he points out that, if proton decay does not occur, then normal matter will spontaneously fuse to iron on a timescale of $10^{1500}$ years, and ...
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Radioactive Dating: How do we know the initial amount of radioactive atoms present in the object?

I'm currently reading a book about Earth's geological history and the authors mentions radioactive dating as on of the methods used to estimate the age of given fossils. It obviously does makes sense ...
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How can integration be used in deriving radioactive decay formula?

I recently learnt the derivation of radioactive decay formula and I am quite surprised about using integration to derive the formula. But $N$ (the number of atoms) can only be discrete numbers (like ...
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The number of active nuclei left after a half life has passed

This is the given statement: A radioactive substance has a half life of 1 hour. Therefore if two nuclei of the substance are present initially, after 1 hour only one will remain undissociated. I ...
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Need help understanding a radioactive decay question

I have the following question: A stationary nucleus of uranium-$238$ undergoes alpha decay to form thorium-$234.$ The following data are available. Energy released in decay $4.27 MeV$, Binding ...
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Why is an alpha particle 'specifically' emitted in radioactive element and not other some other particle? [duplicate]

Why is an alpha particle emitted from any radioactive element if it is decaying? Why can it not emit multiple protons + neutrons one after the other or any other particle that is heavier than an ...
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How do neutrino masses change the shape of the $\beta$ decay spectrum?

It is more-or-less established that neutrinos have masses. But as of now, $\nu$-masses have not been directly measured in the laboratory. But I heard a talk where the speaker said that efforts are ...
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How should I treat background radiation in an experiment?

I am performing an experiment to verify the inverse-square law for the intensity of a beam of $\gamma$ rays emitted by a sample of $^{60}\text{Co}$. The set-up is as follows: A Geiger-Müller tube ...
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Why does the same proportion of a radioactive substance decay per time period? (half life)

Just wondering, if decay is random, why does the activity half every half life, as in, why does it have to reduce by the same proportion in the same time period?
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Is a planet hot inside because it is still hot from beginning, or continuously heated? [duplicate]

If a planet emerges from multiple colliding pieces, that causes its material heat up. Later, an existing planet is continuously heated by radioactive decay, tidal forces and other effects. But are ...
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Half life of radioactive elements: are there some atoms in a different state than others? [duplicate]

I think I generally understand what half-life means. What I wonder is, in a large collection of atoms of a radioactive element, are some atoms more likely to decay than others due to internal state or ...
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Fundamentally, why do some nuclei emit ionizing radiation?

I understand that some nuclei and their isotopes are not stable and therefore at random intervals bits of the nucleus (i.e. protons & neutrons) break away with differing amounts of energy ...
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What to think of the convergence of the logarithmic integral and its repercussions in QM?

Suppose we prepare a certain quantum system with Hilbert space ${\cal H}$, a self-adjoint Hamiltonian operator $H:{\cal H} \to {\cal H}$ whose spectrum is bounded below by $E_0\in \mathbb{R}$ (i.e. ...
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What is the relationship between single and double source gamma radiation?

I am a physics student currently undertaking a labs project about gamma radiation, we measured the spectra of different sources using a scintillation counter, my lab partner and I were wondering if ...
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Is there a working way of accelerating nuclear decay and reducing half life of a nucleus? [duplicate]

Here's a thought for the future cleanup of the environment: find a way to reduce/increase the half life of an element or to accelerate its nuclear decay. Just think, on what factors does the half life ...
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Could fitting a Poisson distribution be better than just counting random events?

When measuring radioactive decays, the easiest way to get their frequency is to just count the number of events and divide by the time recorded. Would instead fitting the distribution of the times ...
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Why most distribution curves are bell shaped? Is there any physical law that leads the curves to take that shape?

All the graphs shown below come from completely different fields of studies and still, they share a similar distribution pattern. Why most distribution curves Bell Shaped? Is there any physical law ...
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What is “average life” in terms of nuclear physics?

I am having a doubt after reading on so many sites. I am not able to understand the clear meaning of average life. Whether it is 36.18 or something else.
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What happens to all the helium produced by alpha-emitting radioisotopes?

Some radioisotopes such as plutonium-238 rapidly produce many alpha particles. According to this, the alpha particles acquire electrons and become helium atoms. 1 mole (238g) of plutonium-238 will ...
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Would a uranium 235 fuel pellet the size of Earth explode?

Imagine a standard $^{235}\text{U}$ pellets scaled to the scale of Earth, I wonder, would it explode or just meltdown? I believe despite overshooting the critical mass, the heat produced is still too ...
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What causes dead time in a Geiger Muller tube?

I’ve been trying to work out if this is to do with electron avalanches caused by the ionisation of the gas in the chamber but can’t find much more online than “the detector needs time to reset”
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How does radiation from a nuclear accident “infect” clothing and people? [duplicate]

In the mini series "Chernobyl" first responders who were exposed to radiation at the scene had to be quarantined. Why? My understanding is that when Uranium 235 fissions it releases nuetrons and ...
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Why is cobalt-57 radioactive? Why isn't it stable?

Cobalt-57 should be the most stable and common isotope of cobalt, right? It has three more neutrons than protons.... Nickel-58 only has two more neutrons than protons, and it is the most common/...
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Is it possible to construct an enclosure with zero ionizing radiation inside? [closed]

Is it possible to construct an enclosure/shield where the Geiger counter would not detect any rays? Or put in another way, is there a location (man-made or natural) on earth where a very sensitive ...
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Is beta decay accelerateable? [duplicate]

Is there any way to alterate weak interaction and thus the rate of beta decay by making it slower or faster? If yes, how? Would radiating some extra bosons or neutrinos, perhaps in a focused beam, ...
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Why spontaneous nuclear fission not classified as a kind of radioactive decay?

In radioactive decays, one considers the alpha, beta, gamma and electronic capture scenarios. Why is the spontaneous nuclear fission not considered as a kind of radioactive decay ?
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Color of radium's glow?

Does the radium salt (or metal for instance) glow only because the emitted alpha particles bombard the nitrogen atoms in the air? Still, how does that lead to a glow anyway? What's the color of the ...
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What is the difference between absorbed dose and kerma?

They both have the same unit, $\frac{J}{kg}$. They both deal with ionizing radiation depositing energy in a medium. But they differ in which energy is being measured and the particles that deposited ...
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Could lead be radioactive?

It was recently discovered in 2003 that Bismuth is radioactive, although it's most stable isotope has a half life orders of magnitudes over the age of the universe. Bismuth has no stable isotopes. Is ...
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Calculating equivalent dose from exposure to radium

My mother was unknowingly exposed to radiation from some radium needles (Ra-226). The exposure was at waist height, from a distance of about 25cm, for a total duration of about 1.25 hours. This ...
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Is the mean life being 1/$\lambda$ a coincidence or a definition?

We were studying radioactivity and after we worked out the half life to be $ln2/\lambda$ the professor then said, this is the average time it takes for half the nuclei to decay to find the average ...
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How do Becquerels relate to Grays?

I understand that becquerels are SI units for curies, and that curies are a measurement of radioactive decays per second. I understand that gray is the measure of uncharged ionizing rays in a sample ...
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Finding general equation for motion of a radioactive particle performing SHM [closed]

Let us assume we have a particle of initial mass $m_{0}$ such that a general time $t$: $$ m(t) = m_{0} e^{- \lambda t} $$ Now, let us say this particle is attached to a spring of spring constant $k$,...
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Is radioactivity a property?

Radioactivity is the physical phenomena where an unstable atom decays and emits a radioactive particle. But is radioactivity a property, I.e. can an atom be radioactive or is it just unstable? Since ...
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1answer
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Superman threw a net with a lot of nukes into the Sun. What happens now? [closed]

The iconic scene in "Superman IV: The quest for peace" shows the eponymous character throwing a net filled with nuclear missles into the Sun. If that were to happen in real life, what would happen as ...
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Radioactive Decay ($dN/dt = - \lambda N$)

The formula for radioactive decay, $$N = N_0 \ e^{- \lambda t}$$ is derived from the following assumption: $$\frac{dN}{dt} = - \lambda N.$$ I understand an assumption has been made that no external ...
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Why does rhenium get a pass on being radioactive? [closed]

Thorium is thought of as radioactive and "dangerous" because its half life is 10 billion years. However, most rhenium is radioactive with a half life of 40 billion years even though rhenium does have ...
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What really causes radioactivity?

We know that a nucleus can transform itself by many ways such as fission, alpha decay, beta decay, etc. But what is it that propels this to happen? Is it just the instability of the nucleus in general?...
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How does positron emission happen naturally? [duplicate]

How does positron-emission happen naturally, for example in Potassium-40? Isn't the added mass of the neutron and the position more than the mass of a proton? Where does the proton get this extra ...
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How can I find a theoretical maximum amount of radioactively polluted water which could be created by a single nuclear reactor?

This question has a lot of tolerance. The current context is that I'm writing a story which involves a group of terrorists who are using the threat of radioactive water pollution to deter ...
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Does decay rate change with time?

In a fire alarm, if we start with americium-241 which emits radiation at 370 kBq (as an example) what will have happened to the decay rate after 470 years (half life is 470 years). The amount of ...
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Is there a mathematical model for predicting when gamma rays are produced in radioactive decay?

My understanding of gamma ray emission from radioactivity is that the daughter particle is in an excited state, which then produces a gamma ray as the electron drops energy levels. In the case of ...
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When are W-bosons emitted?

According to this Wikipedia page W-bosons are involved in beta decay. According to Wikipedia, this occurs when a down quark turns into an up quark and also emits a W− boson. When this happens in a ...
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Is there any non-experimental way to determine what substances are radioactive? [duplicate]

Is there any way to determine if a substance is radioactive and if so, is there any way to determine in what form the radiation will appear, like β- or α-radiation? For example, if I am making a decay ...
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Is there any full Compton scattering experiment done with x-ray since 1923?

The original paper of A.H.Compton 1923 did not provide data of a full experiment; he provided 3 points. Was his result corroborated by others? Can someone provide a real full set of data for Compton ...
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How are energies determined in gamma ray calibration standards?

In operating scintillation gamma ray detectors, certain gamma ray standards are used for calibration: Energy (KeV) Na-22, 511 Mn-54, 835 Co-57, 122 How are ...
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Why are all isotopes of tungsten considered (theoretically) unstable?

The Wkipedia article on tungsten says: Naturally occurring tungsten consists of four stable isotopes ($^{182}\mathrm W$, $^{183}\mathrm W$, $^{184}\mathrm W$, and $^{186}\mathrm W$) and one very ...
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Equivalences for mCi doses and cGy?

I was searching a lot and could only find dosages for curing cancer and allowed emission, but no Iridium 192 dose that could be given internally through brachy sources been found, lets say a 700 cGy ...
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Positron beta decay in stellar core plasma

According to introduction level textbooks $\beta^+$ decay, that is conversion of protons into neutrons only occurs in atomic nuclei. $$p \xrightarrow{\beta^+} n + e^+ + \nu_e$$ I understand that it ...
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Would alpha decay taste sour?

If someone were foolish and/or brave enough to build a device to focus the alpha decay products from a radioactive sample, then point it at their tongue through their open mouth, would it taste sour, ...

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