8B - 21_Radioactivity__11.ppt

8B - 21_Radioactivity__11.ppt - Radioactivity Discovery of...

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Radioactivity Discovery of the nucleus of atoms Radioactive decay
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Radioactivity - Unstable Matter Henri Becquerel discovered radioactivity (1896): A heavy element (U) spontaneously emits radiation. It was soon shown that the radiations are emitted by several elements (Po, Ra,. .) and are of 3 types: α (alpha) - He nuclei (mass = 4 units, charge = 2e units. Rapidly absorbed by materials. β (beta) - electrons (small mass, charge = -1) γ (gamma) - electromagnetic, highly penetrating. Becquerel noted that energy is released (can be MeV per particle). He adds ”the source from which they derive the energy they give off escapes us.” (1903 Nobel Address)
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Detecting nuclear radiation
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Nucleus of Atoms - Radioactivity Ernest Rutherford : α radiation passing through gold foils may scatter through large angles. Explained by the mass of atom concentrated in a small dense volume ; the nucleus.
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How to describe nuclei Z = atomic number = number of protons = # of electrons in neutral atom; determines chemical element. N =
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This note was uploaded on 05/02/2011 for the course PHYS 8B taught by Professor Catherinebordel during the Spring '10 term at University of California, Berkeley.

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8B - 21_Radioactivity__11.ppt - Radioactivity Discovery of...

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