Talk:Rutherford scattering experiments

message: 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)
replies: text: 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)
thread_title: Maths

message: 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)
thread_title:  Ref list 

message: Another good reference is 
* Niaz, Mansoor. "From cathode rays to alpha particles to quantum of action: A rational reconstruction of structure of the atom and its implications for chemistry textbooks." Science Education 82.5 (1998): 527-552. http://websites.umich.edu/~chemstu/content_weeks/F_06_Week4/Thompson_Rutherford_Bohr.pdf 
Niaz emphasizes the critical role of large angle single-scattering as evidence against Thomson atom. To achieve large scattering angles you need a strong force, not possible with multiple scattering from electrons as proposed by Thomson. Johnjbarton (talk) 00:46, 17 May 2024 (UTC)
thread_title:  Another good reference. 

message: The section "A mathematical look at the Thomson model" has a kind of stopping distance calculation based on work and integrals. Rutherford gets the same point across much more simply by balancing the incoming kinetic energy with the potential energy increase as the alpha particle approaches the nucleus head on. On the third page of his 1911 paper, the third equation gives the KE on the right side and the PE on the left. Since the PE is in terms of a stopping distance b and radius R this approach seems clearer to me. Johnjbarton (talk) 02:40, 19 May 2024 (UTC)
replies: text: I added content to Rutherford_scattering#Maximum_nuclear_size_estimate concerning this result. Please check. Johnjbarton (talk) 17:30, 22 May 2024 (UTC)
thread_title:  Balancing kinetic with potential energy. 

message: "The Thomson Model of the Atom" says
* The conservation of momentum and energy for an elastic collision dictate that the angle must be less than 90 degrees if the projectile is more massive than the target. But in the Rutherford scattering experiment, Geiger and Marsden showed that 1 in 8000 alpha particles scattered with angle >90 degrees.
This is the dagger for the Thomson electron scattering hypothesis. It does not tell us what the alternative is, but it eliminates Thomson's model. Johnjbarton (talk) 22:19, 20 May 2024 (UTC)
thread_title:  A different hyperphysics slide 

message: In two places the article uses the metaphor of an "anchor" for inertia. I don't recall ever seeing this in a physics text. An "anchor" implies a tether between two points, one light and one fixed. But as far as we know there is no fixed point or tether.  I don't think this metaphor is harmless but of course others may not agree. I've changed this before but it reappeared. Johnjbarton (talk) 18:03, 21 May 2024 (UTC)
replies: text: If that's how you feel I will change it. Kurzon (talk) 18:08, 21 May 2024 (UTC)
thread_title:  anchored in space by its mass 

message: This section of the article is not properly referenced. It makes claims about a potential source of Rutherford data, Jean Perrin, with no attribution. This is  original research. The rest of the paragraph is similarly improper. History needs references to historians.
@Kurzon Johnjbarton (talk) 23:03, 31 May 2024 (UTC)
thread_title:  Historical measurements of the variables 

message: A couple of times I delete an editorial comment like the phrase following "and" here:
* ...treat it as having infinite mass and ignore the law of conservation of momentum.
Rutherford's scattering model explicitly uses conservation of momentum. When he models scattering from Au, he has one particle, the alpha particle. The Au has "infinite mass" is just another way of saying it is not part of the dynamics. Rutherford equates the angular momentum of the one particle at two points in the trajectory; similarly energy. (The only other fact he uses is the hyperbolic trajectory due to the Coulomb force.) Conservation of momentum is just an accounting fact, like "your savings account balance equals deposits minus withdrawals".
When Rutherford treats recoil for the Al atom, he adjusts his model: two particles exchange energy. But again it's just accounting: the total momentum of the two particles and total energy of two particles. 
His first model does explicitly ignore the transfer of energy and momentum between the alpha particle and nucleus, but that is different from ignoring the "law". Defining the system boundaries in a model -- one vs two particles -- is often the most important step in physics. (Quantum mechanics amounts to the discovery that the classical boundaries don't apply in subatomic systems). Johnjbarton (talk) 03:13, 3 June 2024 (UTC)
replies: text: Thanks, I will take another look at that. Kurzon (talk) 11:18, 3 June 2024 (UTC)
thread_title:  Conservation laws 

message: The content in Rutherford_scattering_experiments#Direct_collision is historically incorrect, is more complicated than it needs to be, and is not referenced. Rutherford's paper gives a much simpler derivation based on potential energy and using his approach can be reference to his 1911 paper. The connection between work integration and potential energy is outlined in
Work_(physics)#Path_independence. A description of Rutherford's approach is in Rutherford_scattering#Maximum_nuclear_size_estimate. Johnjbarton (talk) 02:55, 6 June 2024 (UTC)
thread_title:  Direct collision