AQA A Level Physics 2 Particle Physics

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and p The Photoelectric Effect metal lili When frequency increases, the velocity of the elections are When frequency are not excited enough to escape The energy of the photon is used to: - Provide E = hf = If Ek is 0₂ energy - Give the electron velocity (ie kinetic min + Ex to free the electron (ie the work function () Ek) max is too low, the electrons energy Work function: The minimum = h higher = hf, f ↑ threshhdd frequency (min. freq. for photoelectric effect) energy needed to remove an electron from the surface of a metal. hf = c + Ek 6.63×10 34 x 6.2x10¹4 -3.28x10-20 =$ = 3.78 26x10-19 J Electron Excitation Particle Interactions ! Experienced By charged particks quarks (ie hadrons) Interaction Electromagnetic Strong Weak Gravitational everything everything Identified by photons involved no photons, neutrinos and change of quark flavor. strangeness conserved. neutrinos involved change in quark flavor strangeness not conserved not significant... Quarks? interact via the STRONG FORCE / INTERACTION symbol charge strangeness baryon # + 93e и +3 d ++3 Name ир down strange anti-up anti-down anti-strange S й à 3 Name electron position electron neutrino -13e -te antielectron neutrino muon antimuon - 3e the +3e muon neutrino antimuon neutrino symbol Strangeness in conserved during formation (strong interaction) strangeness changes by -1, 0, +1 during decay (weak interaction) U to IS S Leptons? do NOT interact via strong force/ interaction charge Le Lu +1 -1 Ve Ve М M+ 0 Uμ +1 Du 0 -le +le O 9 +½3 Oo + ! -1/3 +1 - ½ 0 0 -1 +1 -1 Apart from strangeness, EVERYTHING IS CONSERVED. tauons not included in table since they are out of syllabus. HADRONS: (the heavy bois) Particles made of QUARKS & ANTIQUARKS (doesn't matter how Subcategories: Baryon: Baryon # is always 1 Particles made of 3 quarks Proton: und → + charge Neutron: udd ⇒ O charge #15 always 0 No mesons are stable Particles made of I quark & I anti-quark e.g. Meson: Baryon Subcategories: PION (π): KAON (K): meson with NO STRANGE QUARKS e.g. πt: ud Ti: un or dd BOSONS meson WITH STRANGE QUARKS eg. K²: us k Kºds or sd Photon w w zº Gluon Higgs Only Mesons (П, k) FORCES the QUARKS proton is stable π: dù HADRONS FERMIONS K: sū Baryons Leptons (p,n) (e, ve, M...) many) MATTER Let's play a game called Can this decay happen? mesons leptons and mesons (since all mesons decay) the conservation numbers: Charge, Bargon #, LE, Lμ, (Strangeness) Compare LHS & RHS conservation numbers String Can This Decay Happen () { } if (charge, baryon #, LE, Lμ, check out) { if (strangeness checks out and no ventrinos involved) { return "STRONG INTERACTION"; } else { } } else { } " return " WEAK INTERACTION"; return "THIS DECAY CANNOT HAPPEN"; Gauge Bosons: Virtual particles that cause interactions / exerts forces 요요 웃어요 웅 to oto Throw ball Feynman Diagrams! time STRONG Electromagnetic Force WEAK position (Virtual) Photon Gluon W* AFFECTS CHARGED PARTICLES! W, Z Boson W Z electromagnetic force (electrons repel!) Both move back i AFFECTS QUARKS! (Out of syllabus) AFFECTS EVERYTHING! THE 4 WEAK INTERACTIONS (The only 4 Feynman Diagrams you need to know) Beta Minus (8) Beta Plus (*) متعال مع ال d p or d Electron Capture In or d , d P These are the same interaction, just described e n d d p or n er Proton Electron Collision ve In or d W differently e-