Conservation Laws - Particle Physics Reactions Part 3/3 (High School Physics)

[@sFeral]

Quality teaching

[@PhysicsMadeEasy]

Thank you sFeral!

[@sFeral]

3:20 what about the reverse reaction where a neutron is created within the confines of the nucleus ? Is momentum determining spontaneity ?

[@PhysicsMadeEasy]

What determines if a nuclear reaction occurs naturally (to differentiate from feasibility which is what is determined by conservation laws) is the fact that it is energetically favorable or not. In the video, at 3:20, it is a beta minus decay. This is occurs naturally because the mass of a neutron is larger than that of a proton, so it releases energy when it occurs. Beta Plus decay (proton into neutron), needs energy to occur... So it will not happens naturally, you need to provide energy for the reaction to happen.

[@sFeral]

@@PhysicsMadeEasy but that reaction does happen in some unstable nuclei, it's sometimes called "electron capture", that's why I said "within the confines" of a more complex nucleus, apparently the conditions become favorable

[@PhysicsMadeEasy]

@@sFeral Ah, but an electron capture (p + e --> n + neutrino) is not the reverse reaction of a Beta minus decay. It's actually what happens during a supernova when the core of a star collapses into a neutron stars. Your suggestion though makes sense: it is well known that a neutron is "stabilized" by being confined in a nucleus. So, being confined should be a favorable factor to its formation from a proton compared to an isolated neutron. Still, I would need to dig to provide you with a more precise answer.

[@sFeral]

@@PhysicsMadeEasy yes I knew there was a different reaction, and the question is why should there be ? or how does that make sense if n --> p + e + neu , p + e --> n + neu The neutrinos appear to only come out as products, never as reactants (I'm guessing they're different types.. I forget)

[@LukePoon]

Hi, I got every question correct except no 2, could you please explain it to me. Charge of the positive tau is +1, then gamma is zero, and antineutrino tau is zero as well. Then why the answer is possible???😢. Thanks your teaching, it helps me a lot.

[@PhysicsMadeEasy]

Hello Luke, the point of the exercise is to discuss if the reactions are possible or not... You spotted right: the reaction you are mentionning is not possible because charge is not conserved! Well done :-)

[@LukePoon]

Thanks

[@kaushik-sarkar-droid]

Homework done sir 😊 1. NP (not possible). Lepton number not conserved. 2. The second particle i couldn't recognize 🙁. Tau and neutrino i know. 3. NP. Lepton number not conserved. 4. P 5. P. Strangeness not considered as the weak force involved here. 6. P Let me how i did 😀

[@PhysicsMadeEasy]

Hi, sorry to be a little late in reacting. A lot of my plate in my personal life these days! Thanks for giving it a go :-) 1: possible. antimuon gives you a lepton number of -1, and Muonic Neutrino a number of +1, leading to a total lepton number of zero. so it is conserved. B, S and Q are conserved. 2: gamma: it's a photon. This reaction is possible 3: Correct 4: The total lepton number is conserved but not its electronic and muonic components. This reaction is not possible. 5: Correct 6: Correct Questions?

[@kaushik-sarkar-droid]

@@PhysicsMadeEasy Done some silly mistakes 😛, but thank you for the answers with explanations 😊

[@PhysicsMadeEasy]

@@kaushik-sarkar-droid Hey Kaushik, mistakes are the best way one can progress and approach mastery. I can only congratulate you for putting your answers out there!