Talk:Rutherford scattering experiments/Archive 1

Angles
"The result, however, was that the positive particles were repelled from gold foil at very high angles, up to 180 degrees. However, most of the remaining particles were not deflected at all, but rather, passed through the foil." I don't think this describes the results well. I think it should say something like: "The actual result was that a few of the positive particles were deflected at very high angles, up to 180 degrees (that is, reflected back towards the source); but most of them were not deflected at all, but passed straight through the foil." I am digging up memories from decades ago, so I may well be wrong. — Preceding unsigned comment added by Rob625 (talk • contribs) 20:46, 9 November 2011 (UTC)

Concerning the article I read somewhere that after finding wide angles of deflection, Rutherford varied the procedure be bombarding the exposed foil at a 45 degree angle, and was suprised to find some of the deflected particles coming back out of the table plane, which would be a more than 90 degree deflection angle. But the finally developed concept involves the existence of an electrostatic field, which has the capability to absorb and store the kinetic energy of the oncoming charged alpha particle (presumably in electrostatic voltage quantities) and then to give it back to the alpha particle during the remainder of its hyperbolic orbital path. And that isn't the only possible explanation of the charged particle deflection phenomena that could have been proposed for for understanding this subject matter.WFPMWFPM (talk) 18:40, 8 September 2008 (UTC)

Name of article
Should this article not be under Geiger-Marsden experiment with "Gold foil experiment" being a redir? Awolf002 16:49, 7 March 2006 (UTC)


 * I agree. Itub 00:13, 8 March 2006 (UTC)


 * Sounds good to me! --Fastfission 01:02, 8 March 2006 (UTC)

I object

Okay, if nobody else watching this article objects I will go ahead and change it. Awolf002 15:25, 8 March 2006 (UTC)


 * It was certainly called the Geiger-Marsden experiment when I learnt about it at school years ago. Using the "Google test":
 * "Geiger-Marsden Experiment" gets about 400 hits (or sometimes 500, which I don't understand)
 * "Gold Foil Experiment" gets about 11,300 hits (or sometimes 21,200, which I don't understand either)
 * "Rutherford Experiment" seems to be another name for it, and gets about 10,600 hits.
 * "Rutherford Gold Foil Experiment" gets 805 hits.
 * "Rutherford-Geiger-Marsden Experiment" gets a dozen or so hits.
 * On the criteria of "most popular name" then Gold Foil seems to win, although this may not be the correct criteria to use. Jll 15:38, 12 March 2006 (UTC)

I see the same results. However, since I do think we should have "Gold foil experiment" as a redir to "Geiger-Marsden experiment", I'm not certain this helps with this decision. I just think an article name should be 'precise' in the sense that it well describes its own topic, and "Gold foil experiment" seems to be weak. The title of a science article should also be "correct" in the sense that science is using that title as a clear and defined term, so a Google test has only limited value. That criterium might hold for both alternatives, but it still tilts the decision towards the "Geiger-Marsden Experiment" in my mind. Awolf002 01:35, 13 March 2006 (UTC)


 * I don't think it matters too much. I prefer the less colloquial name personally, though I admit part of that reason is that this experiment gets too easily conflated with Rutherford himself and I think Geiger and Marsden deserve a little more visibility. But I recognize that's not a very compelling reason in and of itself! --Fastfission 01:42, 13 March 2006 (UTC)


 * I find the scientific "correctness" argument compelling. Google gets many more hits for Mad Cow disease than for Bovine spongiform encephalopathy, but it is the latter that is used for the title of that article, and I think rightly so. I have changed my view from being unsure to agreeing that the title should be Geiger-Marsden experiment. Jll 16:15, 13 March 2006 (UTC)


 * Alright, I will make the "Gold foil experiment" and "Geiger-Marsden experiment" swap places, as soon as the WP servers are more stable. Right now, editing is quite a pain. Awolf002 17:00, 13 March 2006 (UTC)

It seems as though this idea has been forgotten, and I don't know how to change the title/make a redir. Can someone do it soon?Thatguy1994 (talk) 16:20, 18 May 2010 (UTC)

I learned it as the Rutherford gold foil experiment, but if the title is "gold foil experiment", it won't be ambiguous or cryptic. It's not called The Geiger-Marsden experiment - ANYWHERE. 163.1.229.99 (talk) 23:23, 26 May 2010 (UTC)


 * That's not true. Put it into Google Books and you'll see people have called it that for many decades now. --Mr.98 (talk) 14:16, 4 July 2010 (UTC)

Syntax Error
In the Conclusion section there's an error: "Rutherford came got bored"; Just letting everyone know, I'm changing it, just in case I made a mistake. I'm going to change it to "Rutherford got bored". —Preceding unsigned comment added by 146.86.66.228 (talk) 21:09, 26 April 2008 (UTC)

Some source problems
Is it me or is there very few in-text citations? —Preceding unsigned comment added by Naidevinci (talk • contribs) 03:45, 6 May 2008 (UTC)

Positive charge
The experiment only concluded that there was a charged nucleus. Rutherford's model worked quite well for both a positively or negatively charged centre (he did the calculations) and, though, he knew it was positive he had sufficient intellectual honesty to only report his observations. Waerloeg (talk) 11:38, 1 October 2008 (UTC)

Name change
Since this experiment was led by Rutherford, shouldn't it be named after him? 24.184.200.190 (talk) 05:39, 19 October 2009 (UTC)
 * Probably, but these guys were given a lot of latitude in design. The Moseley experiment would have to be called the Rutherford experiment, too, by the formal reasoning of whose lab it was. Calling these things by the names of the actual workers helps ease confusion in which experiments we're referring to. Geiger-Marsden-Rutherford experiment might be a good compromise. For Moseley, we should probably leave out Rutherford, since I don't think there's much evidence that he participated in the experimental design at all. In the case of Geiger and Marsden, he did actually instruct them before the fact to look for high-deflection alphas. Who knows why; Pais seems to think it was a case of Rutherford's sometimes awesome intuition. S  B Harris 18:14, 18 May 2010 (UTC)


 * Although "Geiger-Marsden" may be the more correct attribution, I think the name "Rutherford experiment" is much more well-known. (Although google tests are not completely indicative, google scholar gives 348 hits for "Rutherford experiment" vs. 27 hits on "Geiger-Marsden experiment", regular google gives 10k vs 4k, so this at least some confirmation that this isn't just me.) Per WP:COMMONNAME, this article should probably be renamed to "Rutherford experiment".TimothyRias (talk) 09:11, 4 October 2010 (UTC)

Diagram is wrong
The collision is shown as a bounce (one straight line, and another just after the bounce). But since both alpha particle and nucleus have a positive charge, they constantly repel each other. The trajectories look more like a hyperbola, where the nucleus constantly deflects the alpha particle, the deflection getting stronger and stronger as the alpha particle approaches. What the diagram shows as a billiard ball collision (particle coming in a straight line, bouncing, coming out in a straight line in the same direction) is actually a curved trajectory, with the inflection point as the collision. 86.194.174.147 (talk) 19:27, 16 August 2011 (UTC)
 * A hyperbola of course LOOKS like two sides of an acute triangle, if you move far enough away (these sides serve as the asymptotes).




 * The question is whether or not the nucleus (or rather the minimum impact parameter radius) is small enough that it looks "very far away." My answer is probably not, if it is as large as shown in the diagram in the Wiki article. Although of course if you make it a correct fraction of the atomic radius (about 1/2000th of it) then any diagram that shows the atom will show the hyberbola coming essentially to the "center" of the atom, and turn will appear hairpin. But yes, you won't see a hairpin if "zoom in" until the minium radius "a" looks as large as you see, which will never happen on atomc scale. This diagram doesn't show that radius (only 1/2000th that of the atom's radius) to scale. S  B Harris 22:13, 16 August 2011 (UTC)


 * I wasn't considering scale, only behaviour. Showing a billiards ball collision hides the Coulomb force, which is how the repulsion (not collision) happens. A billiard balls collision gives the idea that particles shot at the nucleus would just 'bounce' off of it, whatever their charge. Please see Alpha scattering geometry and Rutherford scattering — these pages show hyperbolic paths. 86.202.119.190 (talk) 21:13, 17 August 2011 (UTC)
 * Sorry, but you must consider scale. If you watched an alien spacecraft come into the Solar system aimed nearly at the Sun (say impact parameter only 0.3 AU away) and fall toward the Sun from Neptune around 30 AU, then travel maximally close to the Sun on a hyperbolic escape orbit-- say the 0.14 AU seen 3200 Phaethon (although this is a parabola of course), you'd see a "hairpin turn" at Solar system scale, since the arms of the ingoing and outgoing paths, which would be (essentially) linear except at the very ends, which would involve curves bending from linear only at the scale of closest approach. It wouldn't be an obvious hyperbola, but rather would look very much like a bounce with a kink. Only at scale of 1 AU would you see the hyperbola emerge. S  B Harris 23:53, 17 August 2011 (UTC)

Image suggestion
I'd like to suggest the inclusion of, just to help explain the setup. Tushar Shrotriya (talk) 08:55, 14 February 2014 (UTC)
 * My research into Geiger's papers show that this was not what his apparatus looked like.Kurzon (talk) 16:21, 16 May 2014 (UTC)
 * Fair enough. The image in the conclusions section now looks much better. I had made the suggestion quite a while back when there were no images describing the experimental set-up at all. Tushar Shrotriya (talk) 18:15, 16 May 2014 (UTC)

Nucleus date
In [http://www.amazon.ca/Collected-Papers-Lord-Rutherford-Nelson/dp/1138013668 The Collected Papers of Lord Rutherford of Nelson, Vol 2. p. 23], the author write that the first occurrence of the term nucleus likely was the one in "Radioactive Substances and their Radiation". Reeves (2008) A Force of Nature p. 81 agrees. This is at odds with the reference given for that information. Headbomb {talk / contribs / physics / books} 19:43, 23 July 2014 (UTC)

Suggestions from Featured Article review and Peer review
Both the old Featured Article review and the second Peer review contain useful information on improving this article. Sincerely, Ugog Nizdast (talk) 10:51, 10 October 2014 (UTC)

Plum Pudding
Is the graphic of the Christmas cake really necessary or relevant? — Preceding unsigned comment added by Mt xing (talk • contribs) 18:51, 29 January 2015 (UTC)

A level?
asked me on my talk page "Only B-level? Why not A?  Tell me what is still lacking.".

My answer to this is A-class tend to be reserved for Wikiproject-wide assessments that follows a formal A-class review. Very few projects use them (such as WP:MILHIST), with WP:PHYS not using them (unless the article also falls into the scope of some other project that conducted their own A-class review). So B is the top assessment our articles get without getting more formal reviews. To me, it's clear that the article has considerably improved beyond a C-level article, given the experiment detail included and the visual support, and all or nearly all historical references are not only cited, but mentioned and summarized in prose. To me the article quite clearly meets all six B-class criteria,

But for a more helpful feedback on how the article can be improved in the near-future, the main thing holding this back (content-wise) is the impact it had on subsequent nuclear and particle physics. I won't lie, my impression is that this will be a very challenging section to write, if only because I don't think there are a lot of easily accessible sources that even exist to support the section. This, as far as I am concerned, is the last of the main hurdles to cross for GA/FA levels. With an somewhat expanded section on the legacy of the GM experiments, I think a GA is almost certain following relatively minor tweaks concerning style and general prose.

For FA, it's still falling a bit short of the standard, but that's mostly because I don't yet know how big that legacy section should be, given I haven't made up my mind yet about what exactly the scope of that section should be. The general picture would become a bit clearer once we have a few good sources covering this. The lead also needs to be expanded a bit.

Note: I haven't read things in detail in a while, so not everything in the following paragraph may be relevant or applicable, those are mostly gut-impressions from a quick glance.

Prose also probably needs to be tightened in a lot of places, especially when it comes to making the physical assumptions clear and understandable to the layperson, as well as having all main mathematical results of the GM-related theory, and the actual historical results when possible. Perhaps with a comparison with a modern GM experiment conducted with modern equipment or to a theoretical curve.

Regards, Headbomb {talk / contribs / physics / books} 19:03, 13 April 2015 (UTC)
 * I don't know what you expect, really. Rutherford began nuclear physics.  It was a key discovery which affected all chemistry and physics.  Rutherford's model wasn't perfect and complete and had to be developed further using quantum physics, but isn't that the general narrative of scientific progress?  I can write either too little or too much on this; I don't know what "enough" means.Kurzon (talk) 10:48, 14 April 2015 (UTC)
 * Like I said, I'm not sure what the section should include exactly But I do know that it is underdeveloped. GM experiments started nuclear physics yes, but what exactly was its influence on follow up experiments? You can trace a path from GM experiment to the SLAC Deep Inelastic experiments that discovered quarks, although I'm not sure the section need to go as far as the discovery of quarks. But at the very least, the section needs to detail how doing the same stuff as GM did, using higher energies can probe the structure of the nucleus, and that a deviation from Couloumbian scattering = evidence of strong interactions + estimate for size of the nucleus. E.g. some of this Rutherford scattering. Followed by a mention of later scattering experiments (higher energy scattering using Cockcroft-Walton accelerated α particles? Neutron scattering? electron scattering?) on how they finally nailed the size of the nucleus? Headbomb {talk / contribs / physics / books} 12:04, 14 April 2015 (UTC)
 * What if I never put a Legacy section to begin with? Would you have asked for one?  Perhaps the best way to deal with an underdeveloped branch is to saw it off.Kurzon (talk) 13:57, 14 April 2015 (UTC)
 * I would have requested such a section, yes. Not sure calling it "legacy" is the best section title, but the influence of GM on later physics needs to be addressed with more than a simple mention of "GM launched the start of nuclear physics". The reader needs to know what GM influenced, and at minimum this includes an explanation of Rutherford's limit on nuclear radius (a lot of that is in the Rutherford scattering article), and a discussion of the 3rd graph on the left of this page http://resources.schoolscience.co.uk/STFC/16plus/partich1pg3.html. Headbomb {talk / contribs / physics / books} 14:09, 14 April 2015 (UTC)
 * OK, keep watching the article, as I'll keep working on it.Kurzon (talk) 14:11, 14 April 2015 (UTC)
 * I will. My semester's nearly over, so I should have more time for Wikipedia from now on, but especially from next week onwards. This is one of the articles I was planning to work on, and I'd like to see it get the FA star by the end of summer. I might co-nominate it depending on how involved I get. Headbomb {talk / contribs / physics / books} 14:57, 14 April 2015 (UTC)
 * What I personally think needs work on is the section "Implications of the plum pudding model", which present a mathematical calculation of the maximum deflection an alpha particle will experience using the current known measurements for the dimensions and charges of the particles. What I would like to do is instead use contemporary estimates for these values.  Just how big did Rutherford think a gold atom was?  I've trawled through all his papers and found no values.  It is difficult for me to research this, since I am not a member of a university.Kurzon (talk) 15:50, 14 April 2015 (UTC)
 * Using the most recent values for such a crude estimate wouldn't give you a much more meaningful value. What you consider the radius of gold to be is very much model-dependent, or how exactly you define the "radius" of the electronic cloud surrounding the atom. Atomic_radii_of_the_elements_(data_page) gives the radius as anywhere between 123 and 174 pm. The article seems to be using the covalent radius, or maybe just an old empirical value. Personally, if I was asked to do my own calculation, I'd use either the empirical radius, or just say it's roughly 150 pm to not mislead the reader into thinking this number contains a lot of significant digits. Rutherford's argument hold regardless of it you get 0.01° or 0.02° (or 0.0186°). I notice however, that k is rounded to $8.98$, and that should be $8.99$. Headbomb {talk / contribs / physics / books} 18:11, 14 April 2015 (UTC)

Implications of the plum pudding model
It appears to me that there is something wrong in the statement that Since the electrons are very light compared to the alpha particle, their influence can be neglected[6] and the atom can be seen as a heavy sphere of positive charge, as it is depicted in the figure. It is true of course that the change in linear momentum of a particle hitting a much lighter one is tiny. Therefore in first approximation one may disregard scattering of the alpha from the electrons. But one cannot disregard the charge of the electrons, as it done here. A plum pudding is electrically neutral, hence it produces no Coulomb scattering whatsoever until the charge inhomogeneity originated by the plums is probed by the alpha. I assume this roughly means that only the plums are scattering the alpha, and only when they are sufficiently close.

I am not sure it is worth to obtain quantitatively the deviation predicted by a wrong model, once it is clear that it is incompatible with the experiments. If one were seriously interested, my impression is that the plum pudding would produce even tinier deflections than the actual electrons of real Au ions, which do give rise to small angle scattering. The massive positive pudding is totally cloaked by the plums, the much lighter plums are cloaked by the pudding unless the alpha passes very close.

Am I terribly wrong? If not, this section must be rewritten. One way out is to write that the sketch of an alpha scattering off a much heavier +Ze charge, although not an appropriate picture for the Thomson model, certainly overestimates the deflection angles from the plum pudding, and this estimate already predicts zero particles at right angle to the incoming beam. But is the detailed calculation that follows worth the space? Roberto DR 17:22, 24 September 2015, GMT


 * I based that section and the calculations on what I read here: http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/rutsca3.html Kurzon (talk) 16:36, 24 September 2015 (UTC)

1913 experiment
Shouldn't "magnitude of central charge Qn" be changed to "square of the magnitude of central charge Qn"?

2601:247:4201:1C90:7078:9CCD:8E2B:4CFB (talk) 17:22, 20 September 2019 (UTC)

Maths
Are you good at maths? What do you think of this modification to the equation? The lateral force F exerted on the alpha particle by the gold atom is not constant as the alpha particle crosses the space 2r, so I added something to the start to get the average force exerted. It's unnecessary for this article's needs, but is it correct? Kurzon (talk) 17:08, 31 March 2023 (UTC)

$$ \theta = \arctan \frac{\Delta p}{p} = \frac {2}{\pi} \cdot \left( \int_{-\frac {\pi}{4}}^{ \frac {\pi}{4}} \cos (x)\mathrm{d}x \right) \cdot k \frac{Q_\alpha Q_g}{r^2} \cdot \frac{2r}{v} \cdot \frac{1}{mv}$$


 * The actual correct expression can be seen in the article Impact parameter. But regarding Rutherford's motivation, it's enough to show that the expected scattering angle is very small, and thus the extremely simplified expression to estimate just the order of magnitude would be perfectly sufficient and more appropriate than anything with integrals and trigonometry (which is useless in the small-angle limit). — Mikhail Ryazanov (talk) 02:00, 1 April 2023 (UTC)

Hah. That's the story of my life. Just when I think I have gotten the hang of this math stuff, a real math swot comes along and shows me how utterly hopeless I am. It's the Dunning-Kruger effect. Kurzon (talk) 07:50, 1 April 2023 (UTC)

Now I'd like to do some maths for an alpha particle that goes right through the center of the gold atom. Have I got this right?



The amount of exerted by the gold atom on the alpha particle as the alpha particle approaches is given by

$$\int_{r}^{\infty } k \frac{Q_\alpha Q_g}{x^2} dx = \left [-k \frac{Q_\alpha Q_g}{x} \right ]_r^{\infty} = 2.5315 \times 10^{-16} ~\text{Joules}$$

where x is the distance between the alpha particle and the center of the atom.

The amount of work exerted on the alpha particle as it passes through the atom is given by

$$\int_{0}^{r } k \frac{Q_\alpha Q_g x}{r^3} dx = \left [ \frac{1}{2} k \frac{Q_\alpha Q_g x^2}{r^3} \right ]_0^{r} = 1.266 \times 10^{-16} ~\text{Joules}$$

The total amount of work is 3.797 x 10-16 J.

The initial kinetic energy of the alpha particle is given by

$$E_\alpha = \frac{1}{2} m v^2 = \frac{1}{2} \times 6.645 \times 10^{-27} \times (1.53 \times 10^7)^2 = 7.7776 \times 10^{-13} ~\text{Joules}$$

So the Thomson gold atom does not transfer enough energy into the alpha particle to bring it to a halt, never mind send it flying back to the emitter. Kurzon (talk) 15:20, 10 June 2023 (UTC)

You have a PhD in chemistry. Did I get the above stuff right? Kurzon (talk) 15:54, 27 June 2023 (UTC)

Ref list
1st reference in auto-generated references list doesn’t actually link to the reference in the bibliography. Anyone with a deeper knowledge of wiki templates - is this something specific to this page or is it a wider issue with the template itself? 3nt0 (talk) 00:30, 21 March 2024 (UTC)