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Unformatted text preview: ASTR 100 Lecture 11 17/02/2009 13:57:00 Review: Photoelectric effect Light is a particle --Previously from Young, light is a wave Resolution Came from Einstein in 1905, light comes in small lumps (photon) Quanta (quantumlittle lump of something) Wave packets. Energy in the packets is given by E=hf (f is frequency) H is plancks constant Large continuous wave made of superposition of photons. In 1900 Max planck found the math formula/math description of the black body curve. Atoms throw out radiation (light) with energies given by this formula. E = hf His view: This is a math trick to get black body curve. Nobel prize in 1918 In 1905: to explain the photoelectric effect Einstein: Photons are physically real Nobel prize in 1921 Atomic Structure Goal: Explain emission and absorption line spectra Short History: Democritos (460 BC-370 BC) The idea that matter may be made of small indivisbible pieces atomos atoms Experimental Evidence 1200 1905 Proving this Roger Bacon (1214-1294)------------ J.L. Proust (~1806) Evolutions of the idea: Law of Definite Proportions or the Law of Constant combinations, or the Law of Constant Composition. Also called Prousts Law. What is the law? When you combine elements (stuff), and compounds they always combine in a fixed ratio of masses. E. g. Roger Bacon took mercury (Hg) + Oxygen (O2) Mercuric Oxide 25 : 2 MASS RATIO...
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This note was uploaded on 12/12/2009 for the course ASTR 100Lxg taught by Professor Dappen during the Spring '07 term at USC.
- Spring '07