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Spectra  Chemistry and Doppler Effect

Spectra  Chemistry and Doppler Effect. Lecture 10. Sun’s Spectrum. Sun is not a blackbody. Solar Spectrum. Spectrum of the Sun taken above the atmosphere. Yes, ther e are so many “lines”! Spectral Analysis : Each chemical element produces its own unique pattern of spectral lines.

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Spectra  Chemistry and Doppler Effect

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  1. Spectra  ChemistryandDoppler Effect Lecture 10

  2. Sun’s Spectrum • Sun is not a blackbody

  3. Solar Spectrum Spectrum of the Sun taken above the atmosphere. Yes, there are so many “lines”! Spectral Analysis : Each chemical element produces its own unique pattern of spectral lines.

  4. Kirchhoff-Bunsen Experiment When a chemical substance is heated and vaporized, the spectrum of emitted light exhibits a series of bright spectral lines. Spectroscopy allows to determine the chemical composition of stars and planets!

  5. Kirchhoff’s Laws Law 1 : A hot opaque body, such as a perfect blackbody produces a continuous spectrum. Law 2 : A hot, transparent gas produces an emission line spectrum. Law 3 : A cool, transparent gas in front of continuum source produces an absorption line spectrum.

  6. Sunspot Sun’s average temperature = 6000K Sunspots are about 2000K cooler  appear dark.

  7. Spectroscopy • Spectral lines are like “fingerprint” • Carefully examining spectrum, one can deduce chemical composition of an object. • Spectroscopy = a systematic study of spectra and spectral lines.

  8. Section 5-7 & 5-8 : Any orbits are possible  continuous energy levels • Only certain orbits are possible!  discrete (quantized) energy levels

  9. Hydrogen Atom : allowed orbits for an electron

  10. Light absorption and mission by a Hydrogen atom

  11. Other elements are having more electrons than Hydrogen. • Each of these electron has its own set of orbits (unique spectral lines).

  12. Doppler Effect stationary source moving source

  13. Doppler effect and sonic boom

  14. Doppler Effect The whistle sounds the same no matter where we stand near a stationary train. For a moving train, the sound you hear depends on whether the train is moving toward you or away from you.

  15. Light = Wave • Light = wave : blue light (high frequency), red light (low frequency)

  16. Doppler shift of Stellar spectrum due to unseen planet(s) blue shift : getting closer red shift : getting farther away

  17. First Discovery : 51 Pegasib

  18. In summary… Important Concepts Important Terms Emission/absorption lines Continuum emission Redshift Blueshift • Kirchhoff’s Laws • Spectral lines (discrete energy levels) • Spectroscopy and chemical composition • Doppler effect • Chapter/sections covered in this lecture : sections 5-6through 5-9

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