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Nuclear Physics

Nuclear Physics. Final – Tues 7-10 PM Bring ID. Radiation. Is radiation charged?. Detecting radiation (charged). Fig 44-13a, p.1459. decays – a picture. The Decay Constant. The rate at which a decay process occurs is proportional to the radioactive nuclei present in the sample

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Nuclear Physics

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  1. Nuclear Physics Final – Tues 7-10 PM Bring ID

  2. Radiation

  3. Is radiation charged?

  4. Detecting radiation (charged)

  5. Fig 44-13a, p.1459

  6. decays – a picture

  7. The Decay Constant • The rate at which a decay process occurs is proportional to the radioactive nuclei present in the sample • λ is called the decay constant and determines the rate at which the material will decay • N is the number of undecayed radioactive nuclei present • No is the number of undecayed nuclei at time t=0 half-life

  8. Decay Rate • The decay rate, R, of a sample is defined as the number of decays per second • Ro = Nol is the decay rate at t = o • The decay rate is often referred to as the activity of the sample

  9. Decay Mechanisms

  10. alpha decay

  11. beta decay

  12. The neutrino and the weak interaction A neutron changes Into a proton and electron and neutrino

  13. gamma decay

  14. Changing elements “turning lead into gold” Fig 44-17, p.1465

  15. Carbon Dating • Beta decay of C-14 is used in dating organic materials • The process depends on the ratio of C-14 to C-12 in the atmosphere which is relatively constant • When an organism dies, the ratio decreases as a result of the beta decay of the C-14

  16. A piece of charcoal of mass 25 g is found in the ruins of a city. The sample shows a Carbob-14 acctivity of 250 decays/min. How long has the tree from which the charcoal came been dead. • Half life of carbon-14 is 5730 yr • Fraction of Carbon-14 to Carbon-12 is 1.3x10-12

  17. RADS REM and RBE 1 rad=.01 J/kg of absorbed energy by tissue rem=rad x RBE

  18. Acute Radiation Exposure Effects of Large, Whole-Body Radiation Doses

  19. How much radiation do we get?

  20. Cancer treatment 30 rads

  21. radiation treatmentlinear accelerator

  22. Tracers

  23. Food Fig 45-23, p.1503

  24. NMR (MRI)

  25. MRI

  26. Fig 44-21, p.1469

  27. Tumor

  28. A nucleus of an element has to have a specific charge, but can vary in the number of a. protons. b. neutrons. c. neutrons plus electrons. d. electrons. e. protons plus electrons.

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