|Becquerel has been listed as a level-4 vital article in Science. If you can improve it, please do. This article has been rated as C-Class.|
|WikiProject Physics||(Rated C-class, Mid-importance)|
|WikiProject Measurement||(Rated Start-class, High-importance)|
So how is a becquerel different from a hertz? 188.8.131.52 14:56, 27 Feb 2005 (UTC)
- becquerel are used only in the field of (ionizing) radiation AnyFile 15:37, 3 Mar 2005 (UTC)
The article says:
- It was designated, in the SI, to use the becquerel rather than the reciprocal second for the activity measure unit. This unit was specifically introduced because of the dangers to human health which might arise from mistakes involving the units reciprocal second. Using the becquerel unit a more active (and so, all the other things fixed, more dangerous) source has a higher number. Using 1/s or s as a second instead may lead to confusion.
How so? How would using a unit like, for example, "Emissions per second" (or "eps") result in confusion? A higher number would still indicate greater radioactivity. —The preceding unsigned comment was added by 184.108.40.206 (talk • contribs) 14:23, 19 May 2006.
- That's exactly what a becquerel is; a shorthand for "the activity of a quantity of radioactive material in which one nucleus decays per second". The sentence about proportionality wasn't very clear in the article - I've edited it so it's a bit better, I hope. --HughCharlesParker (talk - contribs) 11:51, 28 February 2007 (UTC)
Example of "typical" levels?
The article does not give any feeling how much is one becquerel? One giga-becquerel? and such.
An example can be one kg of granite (which is a bit more radioactive rock than average), approximately how many becquerels is in it? —Preceding unsigned comment added by 220.127.116.11 (talk) 16:44, 3 January 2010 (UTC)
- 1 Bq = 1 decay per second. 1 GBq would be 109 decays per second. Radioactivity can be measured directly with Geiger counters. Background radiation levels are measured in terms of absorbed doses (see the sievert). To calculate the radioactivity of granite, you would have to know its isotopic composition. -- 18.104.22.168 (talk) 16:52, 27 June 2010 (UTC)
- That is clear, but how do its values correspond to real life? How much an environment radiation of 1 GBq convert to Grays/hour or Rems/hour? What Bq counts of, say, beta radiation are harmless, dangerous to health, lethal? . To calculate precise radioactivity of granite, you would have to know its isotopic composition, but what orders of magnitude should you expect? If you have a Geiger Counter callibrated in Bq, what level displayed on it should get you worried? 22.214.171.124 (talk) 21:39, 30 September 2010 (UTC)
- To give slightly more insight in what values correspond to 'real life', I've added a section about how to calculate the radioactivity in Bq, with an example of 'real life' Potassium radioactivity. Hope this helps. Also I don't think a 'Geiger Counter callibrated in Bq' exists, as it can only count particles that enter the counter itself, and that would depend on the distance between the sample and the counter (and other things). I think what you're looking for is the Sievert. -- joosteto (talk) 17:53, 22 March 2011 (UTC)
- How a given Bq translates to say, Sv, is... complicated.
The short answer is that it doesn't: they measure two entirely different things! You can't say in general that x Bq is harmless and y Bq is dangerous or lethal.
The longer answer is that you can in certain cases determine the dose rate (dose per time: Gy/h, Sv/h) or even dose (for internal exposure) per becquerel, but it's different from nuclide to nuclide and situation to situation. Different nuclides do not just emit different types of radiation, they do so at different energies. You can through experimentation and computer simulation determine the dose rate (dose per time: Gy/h or Sv/h) per Bq of a specified nuclide at a specified distance from a certain specified source geometry (the dose rate at 1 m from an ideal point source of x Bq of a certain nuclide is different than the dose rate at 1 m from a flat 1 m2 surface contaminated with x Bq of the same nuclide).
When an emitter enters the body, it gets even more complicated. Besides the type and energy of the emitted radiation, the dose it delivers will now also depend on where in the body it's absorbed, how long it stays there (biological half-life) and so on, and those factors in turn depend on how it enters the body (e.g. ingestion VS inhalation), and in which chemical form (radioactive atoms form compounds just like stable ones) and physical form (different particle sizes behave differently when inhaled, for example) it's in. Again, though, experimentation and simulation can give estimates on the total dose received in Sv/Bq upon, say, ingestion of nuclide X in chemical form Y.
Sound complicated? It is! It's a whole field of science. Kolbasz (talk) 22:53, 16 November 2011 (UTC)
- How a given Bq translates to say, Sv, is... complicated.
The Wiki entry on banana equivalent dose states this: "A banana equivalent dose (abbreviated BED) is a unit of radiation exposure, defined as the additional dose a person will absorb from eating one banana". According to this it is an absorbed equivalent dose measured in Sv, (78 nSv) so is not relevant to a discussion of activity. The activity of one banana is supposed to be 15Bq, but this is not the BED. AJS126.96.36.199 (talk)
Activity in the case of cascading decay
Say you have a certain quantity of substance A, half-life 10 years, which decays into substance B, half-life 10 seconds. The total activity is about double the activity of A, since each disintegration of an atom of A is almost immediately followed by a disintegration of the newly formed atom of B.
Is there any standard way to express such a situation, which I think is quite common? If you just say "I have 1000 Bq of A", counting only the disintegrations of atoms of A, that is misleading, since you actually have about 2000 disintegrations per second.
- Check out the wiki articles on secular equilibrium and transient equilibrium. But you're absolutely right - if any of the daughter nuclides are also radioactive, the total activity of the sample you're looking at will become higher. Whether you bother to state the daughter nuclides' activities as well or just the mother nuclide's depends on the application. Kolbasz (talk) 20:04, 14 November 2011 (UTC)
4400 becquerels from decaying potassium-40
I was looking for a source for this statement, but all I can find are internet postings that seem to be a copy-paste of this wikipedia article.
However, doing some simple math the average human body contains 160 grams of potassium-40 at 31 becquerels / gram gives an average of 4960 becquerels. However, it would be nice to find a formal source. The banana equivalent dose article could use a similar source.--RaptorHunter (talk) 21:47, 24 May 2011 (UTC)
- That's 160 g (and 31 Bq/g of 40K) of natural potassium, not potassium-40 - the specific activity of potassium-40 is 2.54·105 Bq/g. And TBH, the spread is such that the potassium-40 content of the human body should probably just be stated as "around 4-5 kBq". Kolbasz (talk) 19:22, 14 November 2011 (UTC)
The Wiki article on Potassiunm gives a reference quoting 120g of potassium in a 60kg adult. In these days of galloping obsesity this might seem to be unrepresentative in some countries, but multiplying by 31Bq gives 3.72kBq for a rather light-weight adult. AJS 188.8.131.52 (talk) —Preceding undated comment added 14:58, 5 February 2014 (UTC)
Example in article appears incorrect
The article states:
"For instance, one gram-mole of potassium contains 0.0118 gram of 40K (all other isotopes are stable) that has a t1/2 of 1.248×109years=39.38×1015 seconds, and has an atomic mass of 39.963 g/mol, so the radioactivity is 3.2 kBq."
The calculation using these figures is correct, but I think that the quantity of potassium-40 is incorrect. Other Wikipedia pages, e.g. "Banana equivalent dose" and "Potassium" give 0.0117% K-40. Using that figure I get 0.00457 gram K-40 per gram-mole potassium, giving 1.14 kBq.
As this is not my area of expertise I would like someone else to check this and make any necessary corrections.
"Radiant exposure" seems more appropriate than "Fluence"
In the section "Radiation Related Quantities" the table's row for the quantity Fluence (Φ) seems inappropriate, due to imprecision and inaccuracy. Fluence in physics is a flow during time, but in medicine it's a flow through an area. Becquerels of radiation are more relevant to medicine, but in that field the measurement is "more properly referred to as radiant exposure". Radiant exposure in photometry is visible light, which becquerels of radiation usually are not; the radiometric metric is more appropriate. So the precise "fluence" of radiation that's measured in becquerels is "radiant exposure", not the ambiguous "fluence". Radiant exposure is symbolized by He, indicating joules per square meter (J/m2). The table instead gives reciprocal area (cm-2 or m-2), which is radiometry's concern, but missing the energy component.
So I propose changing that row to instead document Quantity: radiometric exposure; Name: radiant exposure; Symbol: He; Unit: joule per square meter. That rendering is consistent with the radiant exposure article's table of SI radiometry units. However, since it's a derived quantity and unit rather than one with a proper name, I haven't found a year in which it was introduced, so I'd leave that blank.
- Delacroix, D.; Guerre, J.P.; Leblanc, P. & Hickman, C. (2002). Radionuclide and Radiation Protection Handbook (2nd ed.). Nuclear Technology Publishing.