330 likes | 431 Views
Announcements. Grade Breakpoint Adjustment Exam 4 Final Exam Multiple choice (16 questions) Problems like problems on midterms Problems from midterms with different numbers. Fusion--Two nuclei combine to form a heavier nucleus. First reaction in early stars
E N D
Announcements • Grade Breakpoint Adjustment • Exam 4 • Final Exam • Multiple choice (16 questions) • Problems like problems on midterms • Problems from midterms with different numbers
Fusion--Two nuclei combine to form a heavier nucleus First reaction in early stars 11H + 11H → 21H + e+ + νe mass before - mass after = energy released/c 2 (2MH1 – 2Me) – (MH2 –Me + Me) = (2x1.0078250u - 0.0005486u) - 2.0141018 u = 0.0009996 u (1uc2=931 MeV) Q = 0.93 MeV
Fusion--Two nuclei combine to form a heavier nucleus More reactions in stars 11H + 11H → 21H + e+ + νe 11H+ 21H → 32He 11H+ 32He → 42He + e+ + νe 32He+ 32He → 42He + 11H + 11H
Fusion--Two nuclei combine to form a heavier nucleus One reaction in a hydrogen bomb 21H + 31H → 42He + n Total mass before -Total mass after = energy released 5.0302 u - 5.0113 u = .0189 u ≈ 17.6 MeV
Fusion Reactors • Much less radioactivity • Mostly produces helium-4, but materials near the reaction can absorb neutrons, etc. • Hydrogen is everywhere! • It doesn’t work . . . Yet • Protons repel each other until you get them really close • Really high temperatures needed
Other practical uses of nuclear physics… • Nuclear medicine • Nuclear treatment (destroy tumors) • Tracer imaging • PET scan • NMR (MRI) ? • Power for space probes • Dating materials • Sterilization of equipment or food • Smoke detectors
Van Dyck’s “Saint Rosalie Interceding for the Plague-Stricken of Palermo” Irradiated with neutrons Detected electrons emitted
After a few hours - manganese (found in umber, A dark pigment)
After 4 days - phosphorous (found in charcoal)
Jackson Pollock – Galaxy Irradiated with neutrons
Jackson Pollock – Galaxy Detected secondary emission of truth
And beyond • Particle physics, QCD, the standard model • Unification theories / theory of everything • String theory
3 Nephi 12:3 Yea, blessed are the poor in spirit who come unto me, for theirs is the kingdom of heaven. Brothers and sisters, whatever your distress, please don’t give up and please don’t yield to fear. --- Elder Jeffrey R. Holland, General Conference, April 2006
Review Request • deBroglie wavelength for relativistic particle of given Ek
Review Request • Velocity transform
Review • Postulates of Relativity • Time dilation • Length contraction • Lorentz transformations – velocity transform • Relativistic momentum and energy
Review • Photons • Bohr Atom • de Broglie Waves
Review • Notation – atomic number, mass number • Half Life
Review • Nuclear Decay • Gamma • Beta – • Beta + • Ec • Alpha
Review • Fission • Fusion