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Waves and Particles: Electrons in Atoms

Explore the concept of waves and particles, wavelengths and frequencies, and the energy of photons in the electromagnetic spectrum. Learn about quantum theory and the wave-particle duality.

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Waves and Particles: Electrons in Atoms

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  1. I. Waves & Particles(p. 117-124) Ch. 5 - Electrons in Atoms C. Johannesson

  2. A. Waves • Wavelength () - length of one complete wave • Frequency () - # of waves that pass a point during a certain time period • hertz (Hz) = 1/s • Amplitude (A) - distance from the origin to the trough or crest C. Johannesson

  3. crest A A origin trough  A. Waves greater amplitude (intensity) greater frequency (color) C. Johannesson

  4. B. EM Spectrum HIGH ENERGY LOW ENERGY C. Johannesson

  5. R O Y G. B I V red orange yellow green blue indigo violet B. EM Spectrum HIGH ENERGY LOW ENERGY C. Johannesson

  6. B. EM Spectrum • Frequency & wavelength are inversely proportional c =  c: speed of light (3.00  108 m/s) : wavelength (m, nm, etc.) : frequency (Hz) C. Johannesson

  7. WORK:  = c   = 3.00  108 m/s 4.34  10-7 m B. EM Spectrum • EX: Find the frequency of a photon with a wavelength of 434 nm. GIVEN:  = ?  = 434 nm = 4.34  10-7 m c = 3.00  108 m/s = 6.91  1014 Hz C. Johannesson

  8. B. EM Spectrum • What happens to the frequency if the wavelength is shorter? • Try calculating the frequency if the wavelength is 405nm. C. Johannesson

  9. C. Quantum Theory • Planck (1900) • Observed - emission of light from hot objects • Concluded - energy is emitted in small, specific amounts (quanta) • Quantum - minimum amount of energy change C. Johannesson

  10. Classical Theory Quantum Theory C. Quantum Theory • Planck (1900) vs. C. Johannesson

  11. C. Quantum Theory • Einstein (1905) • Observed - photoelectric effect C. Johannesson

  12. C. Quantum Theory • Einstein (1905) • Concluded - light has properties of both waves and particles “wave-particle duality” • Photon - particle of light that carries a quantum of energy C. Johannesson

  13. C. Quantum Theory • The energy of a photon is proportional to its frequency. E: energy (J, joules) h: Planck’s constant (6.6262  10-34 J·s) : frequency (Hz) E = h C. Johannesson

  14. C. Quantum Theory • EX: Find the energy of a red photon with a frequency of 4.57  1014 Hz. GIVEN: E = ?  = 4.57  1014 Hz h =6.6262  10-34 J·s WORK: E = h E = (6.6262  10-34 J·s) (4.57  1014 Hz) E = 3.03  10-19 J C. Johannesson

  15. C. Quantum Theory • Violet light has a frequency of 7.41x1014Hz, does it have more or less energy than red light? C. Johannesson

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