2010 PHYSICS 002C Lecture 26

2010 PHYSICS 002C Lecture 26 - PHYSICS 002C Lecture 26 May...

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Lecture 26 May 28, 2010 Serway and Jewett Chapter 30 – Nuclear Physics Preamble Who cares about nuclear physics? Especially for biologists, for whom it would seem that the relevant size objects are enzymes (10 nm) or a people (1m), learning more about the nucleus (1fm) than its charge Z and atomic mass A is going too far! Maybe not. For example, except for the actual and perceived biological hazards of radioactive waste, nuclear power would be the solution to the energy problem [foreign oil, depletion of fossil fuels, rising levels of pollution, CO 2 levels, etc.]. Nuclear magnetic resonance imaging (MRI) is a great way to see the chemical and physical structure of a human body with sub-mm resolution. Subatomic particles are used for killing tumor cells, and muons are proposed by UCR’s Prof. Nagamine as a relatively noninvasive probe of brain function. Neutrons are widely used for measuring properties of biomaterials via neutron scattering. Radio isotopes P 32 , H 3 (tritium), and S 35 are commonly used in bio labs to trace the components of chemical reactions and to separate proteins (Southern blotting) and DNA. Positron emission tomography ( PET ) uses O 15 , F 18 , N 13 , C 11 to locate and image hungry tumors in the brain and as an alternative to computed x-ray tomography (CAT) scans for diagnosis of ischemia. A. Turkevich Rutherford backscattering , invented by Anthony Turkevich (1916-2002) is used to tell the elemental surface composition of a rock or other sample. “Surveyors V, VI, and VII were successful, and all three carried Tony’s analytical devices: foremost, an alpha-particle backscattering instrument that not only gave us the first complete elemental composition of the lunar surface but also showed that the Moon is a differentiated body, not a homogeneous conglomerate such as a giant chondrite, which was the prevailing view at that time. Surveyor V, landing on September 11, 1967, at Mare Tranquillitatis, showed that there are basalt-like materials—essentially cold lava on the lunar surface.” Biographical memoir, National Academy of Sciences, 2007 Rutherford backscattering If the target nucleus has mass number A , an alpha particle ( A =4) of energy E 0 will backscatter with energy 2 0 4 4 A A E E . Besides all this, it is good to be informed about topics that other people might use to make you do what they want if you are credulous, and to have some inkling of how the world is framed and what are its immutable laws and how amazing it is that there are living creatures courageous enough to subject their sacred hypotheses to the arbiter of truth. Q : What is the arbiter of truth? (a) Mathematical theory; (b) Experiment; (c) Writings in a sacred book; (d) Opinion polls; (e) The Courts. Backscattered energy vs.
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This note was uploaded on 09/23/2010 for the course PH 02c taught by Professor Mile during the Spring '04 term at Riverside Community College.

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2010 PHYSICS 002C Lecture 26 - PHYSICS 002C Lecture 26 May...

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