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3 - The Particle Nature of Light

3 - The Particle Nature of Light. The “Ultraviolet Catastrophe”. 1900 Max Planck - E = hf or E=h  1905 Einstein - “ Photons ” Wave-Particle Duality. Continuum & Lines 1814 - Joseph Fraunhofer discovers spectral lines in the spectrum of the Sun. 1859 - Robert Bunsen & Gustav Kirchhoff:

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3 - The Particle Nature of Light

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  1. 3 - The Particle Nature of Light

  2. The “Ultraviolet Catastrophe”

  3. 1900 Max Planck - E = hf or E=h 1905 Einstein - “Photons” Wave-Particle Duality

  4. Continuum & Lines 1814 - Joseph Fraunhofer discovers spectral lines in the spectrum of the Sun.

  5. 1859 - Robert Bunsen & Gustav Kirchhoff: every chemical element, when heated, gives off a unique set of bright spectral lines Calcium Iron Sodium

  6. Kirchhoff’s laws: 1. A hot, glowing (condensed) object emits a CONTINUOUS spectrum. 2. When a heated gas is viewed against a dark, cool background (i.e., not a bright continuum), BRIGHT EMISSION LINES are seen. 3. When a continuous spectrum is viewed through a cooler gas, DARK ABSORPTION LINES appear in the continuous spectrum.

  7. Spectroscopy and Atomic Structure 1910 Ernest Rutherford - 99.98% of mass of the atom is in a small dense nucleus.

  8. 1885 J.J. Balmer finds that the spectrum of hydrogen follows a precise mathematical relation:

  9. 1914 Niels Bohr derives structure H atom from quantized angular momentum Each element has a different orbital structure and spectrum (see Java applet - online notes)

  10. Molecular Spectra Rotational Vibrational Electronic

  11. SiO

  12. Earth’s Atmosphere

  13. CO in Jupiter

  14. CO in the Red Rectangle

  15. Solids - no rotation But other types of transitions allowed - useful for making colored filters Can study chemical compositions of solids using transmission ( and reflectance) spectroscopy

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