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Gustav Robert Kirchhoff

Gustav Robert Kirchhoff. A Brief Digest of His Life and Work by Mike Rasmussen. Vital Statistics. Born: 12 March 1824, Königsberg, Prussia Christened: 11 April 1824 Father: Friedrich Kirchhoff (lawyer) Mother: Johanna Henriette Wittke

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Gustav Robert Kirchhoff

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  1. Gustav Robert Kirchhoff A Brief Digest of His Life and Work by Mike Rasmussen

  2. Vital Statistics • Born: 12 March 1824, Königsberg, Prussia • Christened: 11 April 1824 • Father: Friedrich Kirchhoff (lawyer) • Mother: Johanna Henriette Wittke • Married: 1847, to Clara Richelot (his math professor’s daughter – good reason to study math!) • Died: 17 October 1887, Berlin • Temple work: Done several times, 1929-2001. (Often just sealed to Mr. and Mrs. Kirchhoff – good reason to study physics!)

  3. Scientific contributions in brief • Kirchhoff’s Law (Thermodynamics) • Kirchhoff’s Circuit Laws • Spectroscopy (with Bunsen) • Fresnel-Kirchhoff diffraction formula.

  4. Kirchhoff’s Law (Thermodynamics) • At thermal equilibrium, light emitted equals light absorbed. • (Otherwise it wouldn’t be at equilibrium.) • So, black bodies are great emitters. • And “Space Blankets” are good at not emitting.

  5. Kirchhoff’s Circuit Laws • The Sum of voltage rises and drops around a loop equals zero. • (Energy is conserved.) • Currents entering a junction are equal to currents leaving a junction. • (Charge is conserved, similar to thermodynamic law. Remember, a lot of people thought charge was like heat, and might accumulate at a junction.) • So, we can do circuit analysis. • Obvious, but useful – maybe we can all get laws named after us someday!

  6. Kirchhoff and Bunsen

  7. Spectroscopy “Two old telescopes, a prism, and a cigar box”

  8. A Great Spectroscopy Experiment • Burned highly purified sodium, observed two strong yellow lines • Lit a Drummond light, which is a stick of lime heated by a flame to white hot – it radiates nearly as a black body, with no dark lines • Lit a sodium flame in between the “limelight” and the spectroscope, and observed two dark lines – the sodium absorbed more energy than it emitted

  9. Spectroscopy results • Identified Fraunhofer’s yellow lines in several lamp spectra as sodium emission • Identified Fraunhofer’s dark lines in the solar spectrum as absorption • Identified the chemical content of the sun • Identified Cesium and Rubidium

  10. Fresnel-Kirchhoff diffraction formula. • Fresnel derived a formula for diffraction by applying Newton’s calculus to Huygen’s wavelets. • In 1887, Kirchhoff used Maxwell’s Equations to justify Fresnel’s formula. • Hence, it was named after both Fresnel and Kirchhoff. • Apparently, it killed him, as he died that year.

  11. References • http://en.wikipedia.org/wiki/Gustav_Kirchhoff • www.familysearch.org • http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Kirchhoff-Bunsen-1860.html • http://www.neatherd.org/astronomy/Fingerprints%20of%20light.htm • http://optics.byu.edu/Textbook.htm

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