Quantum Mechanics - Discovery of radioactivity In 1896, a...

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Discovery of radioactivity In 1896, a French physicist Henri Becquerel, (accidentally) discovered that uranium salts affected photographic plates, even though the plates were covered Some radiation was being emitted by the uranium that was very penetrating In fact, some of the uranium atoms were decaying and in the process emitting the radiation Atoms were not always stable, as had previously been thought
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Atoms are not fundamental Enter JJ Thomson In the late 1890’s, JJ did experiments using cathode ray tube By 1895, he discovered that the cathode ray particles were electrons coming out of atoms We had been using electricity for some time in our cities by 1895, but did not know that an electric current was the flow of electrons since we didn’t know about electrons
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Meanwhile, back at the lab Wilhelm Roentgen accelerated electrons in an evacuated glass tube and found that x-rays were produced X because they were unknown caused undeveloped photographic film to be exposed suspicion was that they were some sort of EM radiation, of very short wavelength Mrs. Roentgen, the frst test subject
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X-rays In fact, x-rays are EM radiation of wavelengths of order of 1nm or less
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DNA For example, how was the structure of DNA determined? Since the atoms are spaced by about 1 Angstrom apart, then use X-rays of wavelength 1 Angstrom (0.1 nm)
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Rosalind Franklin “As a scientist Miss Franklin was distinguished by extreme clarity and perfection in everything she undertook. Her photographs are among the most beautiful X-ray photographs of any substance ever taken. Their excellence was the fruit of extreme care in preparation and mounting of the specimens as well as in the taking of the photographs. “ cross pattern of X-ray
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This note was uploaded on 10/17/2011 for the course ECON 101 taught by Professor Thompson during the Spring '11 term at Michigan State University.

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Quantum Mechanics - Discovery of radioactivity In 1896, a...

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