Lecture07 - Lecture #7: Radiation and Spectra II How is...

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1 Astro 102/104 1 Lecture #7: Radiation and Spectra II • How is light absorbed and emitted? How is light absorbed and emitted? – Models of Atomic Structure. Models of Atomic Structure. – Formation of Spectral Lines. Formation of Spectral Lines. – Doppler Shift. Doppler Shift. • Applications in Solar System Studies Applications in Solar System Studies – Detecting gaseous phases (atmospheres, stars). Detecting gaseous phases (atmospheres, stars). – Detecting solid phases (ices, minerals). Detecting solid phases (ices, minerals). Astro 102/104 2 The Main Point Astronomers use spectroscopy , the study of the interaction of light and matter, to determine what planetary surfaces and atmospheres are made of. Astro 102/104 3 How do light and matter interact? • The interaction occurs at the atomic scale. • Therefore, understanding the interaction means understanding the atom. • But the realm of the atom is at a scale that is completely outside our intuitive experience. • So scientists have devised models of the atom, to try to grasp what's going on. Astro 102/104 4 Subatomic Particles • J.J. Thomson discovered the existence of electrons in 1897. • He used a cathode ray tube to show that particles appeared to be carrying negative charge. • Since atoms are neutral, these particles must represent only one part of the atom, whose charge must be balanced by something else. • Wild! Controversial! "Could anything at first sight seem more impractical than a body which is so small that its mass is an insignificant fraction of the mass of an atom of hydrogen?" -- J.J. Thomson.
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2 Astro 102/104 5 Subatomic Particles Ernest Rutherford devised an experiment in 1911 and discovered the
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Lecture07 - Lecture #7: Radiation and Spectra II How is...

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