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## Blackbody Radiation

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**Blackbody Radiation**Presented by Group 6: Neal Boseman, Vessen Hopkins, and Sarah Moorman**Topics of Discussion:**• What is Blackbody Radiation? • History of Blackbody Radiation • How has this discovery impacted Modern Physics? • Applications of Blackbody Radiation**Gustav Kirchhoff**• German physicist • 3/12/1824 – 10/17/1887 • Contributed in the Areas of: - Electrical Circuits - Spectroscopy - Blackbody Radiation Image Credit: Hulton Archive/Getty Images**Spectroscopy**• Spectroscopy - is the scientific study of an object based on the dispersion of said object’s light into its component colors.**Kirchhoff’s Laws**• Hot, dense object will produce a Continuous Spectrum. - This is what Kirchhoff termed a Blackbody. • Hot, low density object will produce an Emission Line Spectrum. • A cool, low density gas in front of a continuous light source will produce an Absorption Line Spectrum.**Blackbody**• Theorized in 1859 by Gustav Kirchhoff. • An ideal physical body. • Absorbs 100% of all incident radiation and reflects or transmits none. • Emits 100% radiation. Image Credit: NASA**Blackbody Radiation**• A Blackbody in thermal equilibrium emits EM radiation termed Blackbody Radiation. • Universal Property: Independent of material used. • Led to relation between radiation intensity (I), temperature (T), and wavelength ( λ ). • Blackbody Curves • Helped prove thermal radiation was also EM radiation. • Many physicist attempted to characterize shape of Blackbody curve…**Blackbody Radiation**Image credit: http://hyperphysics.phy-astr.gsu.edu**Attempts to Find Best Fit Formula**• Wien’s Displacement Law: • Relation between peak wavelength and temperature. • Stefan-Boltzmann Law: • Relation between temperature and the power per unit area. • Rayleigh-Jeans Formula: • Relation between radiation intensity, temperature, and wavelength. • Ultraviolet Catastrophe!**Raleigh-Jeans Law**Image credit: http://hyperphysics.phy-astr.gsu.edu**Failures to Model Blackbody Curves**• Rayleigh-Jeans Formula • Rayleigh-Jeans model failed to comply with experimental data at high frequencies • Wien’s Radiation Law • Wien's model failed to comply with experimental data at low frequencies.**Max Planck**• (Apr. 1858 to Oct. 1947) • Approach to Blackbody Radiation Problem • Planck’s Radiation Law • Mathematical Trick • h = Planck’s Constant • Discrete Values of Energy: E = nhf Image credit: Hulton Archive/Getty Images**How Did Blackbody Radiation Impact Modern Physics?**• Led to established relationships between light intensity, wavelength, and temperature: • Wien’s Displacement Law • Stefan-Boltzmann Law • Rayleigh-Jeans Formula • UV Catastrophe • Planck’s Radiation Law • Discrete Values Led to Best Fit for Experimental Data – Planck’s Mathematical Guess • Thus We Have Quantization of Energy: E = nhf • Implications for What’s Occurring at Atomic Level. • Birth of Quantum Mechanics!**Applications of Blackbody Radiation**• Gave people the ability to calculate temperatures of distance cosmic bodies • Inspired new devices such as thermal vision and new types of thermometers**Acknowledgements/References**• Thornton, Stephen T., and Andrew F. Rex. "The Experimental Basis of Quantum Physics."Modern Physics for Scientists and Engineers. 4th ed. Boston, MA: Cengage Learning, 2013. N. pag. Print. • Kirchhoff, G. (1860). "Ueber das VerhältnisszwischendemEmissionsvermögen und demAbsorptionsvermögen der KörperfürWärme and Licht". Annalen der Physik und Chemie109 (2): 275–301.Bibcode:1860AnP...185..275K. doi:10.1002/andp.18601850205. Translated by Guthrie, F. as Kirchhoff, G. (1860). "On the relation between the radiating and absorbing powers of different bodies for light and heat". Philosophical Magazine. Series 4 20: 1–21. • Planck, Max (1901). "On the Law of Distribution of Energy in the Normal Spectrum".AnnalenderPhysik4: 553. Bibcode:1901AnP...309..553P.doi:10.1002/andp.19013090310. • Fowler, Michael. "Planck’s Route to the Black Body Radiation Formula and Quantization." Lecture. 25 July 2008. Web. 1 Dec. 2013.