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Chapter 2

Chapter 2. Spectroscopy / Review . Outline. Test Wednesday Spectroscopy Check posted grades!. Misc. If you received a C- or below (or any grade you have questions about) for your mid-term grade, please come by my office to discuss your situation. Lab notes. No Inside lab this week

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Chapter 2

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  1. 1

  2. Chapter 2 Spectroscopy / Review 2

  3. Outline • Test Wednesday • Spectroscopy • Check posted grades! 3

  4. Misc • If you received a C- or below (or any grade you have questions about) for your mid-term grade, please come by my office to discuss your situation. 4

  5. Lab notes • No Inside lab this week • Constellation presentations soon. This is an individual lab. • Picture • How to find it • Interesting objects • History/Mythology • Participation 5

  6. Lab notes • Report Lab options. This is a group lab. • Track the Sunset (Sunrise) • Track the Moonrise (Moonset) • Track the motion of (Mars, Jupiter, Saturn) against the background stars • Track the moons of Jupiter (Saturn) • Track sunspots • Dark Sky star count • Other labs that you think up 6

  7. Test Topics • Chapter 0 - review • Chapter 1 - review, and add • 1.3 Kepler • 1.4 Newton • Chapter 2 - review, and add • 2.4 Blackbody radiation • 2.5 Spectroscopy • Chapter 4 - The Solar System • 4.1 inventory (review general properties) • 4.2 debris (asteroids, meteoroids, comets) • 4.3 solar system formation (nebular theory) 7

  8. Test Topics • Chapter 5 - Earth and Moon • Entire chapter (particularly atmospheres) • Chapter 6 - Terrestrial Planets • 6.3 and 6.8 atmospheres (supplement to 5.3) • Other sections - just a quick read, on your own. • Chapter 7 - just a quick read, on your own. • Review questions on-line 8

  9. Photon energy • The energy of a photon (a packet of light) is directly proportional to the frequency of the photon. • High frequency means high energy • Double the frequency means double the energy of the photon. 9

  10. Figure 2.10Blackbody Curves • Note the logarithmic temperature scale. • For linear scale, go look at the “black body” section of: http://solarsystem.colorado.edu/ • example - oven 10

  11. Stefan’s Law • Total energy radiated (from each m2 of surface area) is proportional to the fourth power of the temperature (T)4. • And the Stefan-Boltzmann equation: F = sT4 • (here F is Energy Flux) 11

  12. Small Group Exercise • A pulsating variable star has a temperature ranging from 4000 K to 8000 K. • When it is hottest, each m2 of surface radiates how much more energy? recall: F = sT4 12

  13. A pulsating variable star has a temperature ranging from 4000 K to 8000 K. When it is hottest, each m2 of surface radiates how much more energy? A) (sqrt2)x more B) 2x more C) 4x more D) 16x more 13

  14. A pulsating variable star has a temperature ranging from 4000 K to 8000 K. When it is hottest, each m2 of surface radiates how much more energy? A) (sqrt2)x more B) 2x more C) 4x more D) 16x more 14

  15. Group Activity • You have just baked a cake at 175C, and a Pizza at 220C. • How much more energy is radiated from the Pizza? 15

  16. Group Activity • You have just baked a cake at 175C, and a Pizza at 220C. • How much more energy is radiated from the Pizza? • convert from C to K 16

  17. Group Activity • You have just baked a cake at 175C, and a Pizza at 220C. • How much more energy is radiated from the Pizza? • convert from C to K • use Stefan’s Law F=sT4 17

  18. Group Activity • You have just baked a cake at 175C, and a Pizza at 220C. • How much more energy is radiated from the Pizza? • convert from C to K • use Stefan’s Law F=sT4 • compare values using a ratio (pizza/cake) 18

  19. How much more energy is radiated by the pizza at 220K than the cake at 175K? A) 1.11x more B) 1.26x more C) 1.47x more D) 16x more 19

  20. How much more energy is radiated by the pizza at 220K than the cake at 175K? A) 1.11x more B) 1.26x more C) 1.47x more D) 16x more 20

  21. Spectroscopy 21

  22. ROY G BIV 22

  23. ROY G BIV • red • orange • yellow • green • blue • indigo • violet 23

  24. Figure 2.11Spectroscope 24

  25. Figure 2.12Emission Spectrum 25

  26. Figure 2.15Absorption Spectrum 26

  27. Figure 2.16Kirchhoff’s Laws 27

  28. Figure 2.13Elemental Emission 28

  29. Figure 2.14Solar Spectrum 29

  30. But where do those lines come from? 30

  31. Background • At the end of the 19th century, many scientists believed that they had “discovered it all” and that only details remained to be filled in. (Like why are those spectral lines there.) • Electromagnetic energy appears to come in “packets”, called photons. • Particle nature of photons helps explain interactions with matter. • Photon energy is directly proportional to frequency. 31

  32. Quantum Mechanics (How to build an atom) 32

  33. How to Build an Atom • Components • Proton - heavy, positive charge • Neutron - heavy, no charge • Electron - light, negative charge • Number of protons defines element type (atomic number) • Sum of protons and neutrons defines atomic weight 33

  34. How to Build an Atom • Almost all atom mass is in the nucleus (protons and neutrons) • Protons are held together by nuclear force. (Very strong, but very short range.) • Protons (positive charge) make an “electromagnetic potential well.” (Attracts negative charges.) • Electrons (negative charge) are attracted to the well and “fill it up” until you end up with a neutral atom. 34

  35. Figure 2.18Modern Atom - note electron “cloud” 35

  36. Some Rules for Atoms • No two electrons can be in the same state of the same atom at the same time. • Only certain energy levels are allowed. • Only photons with the same energy as the difference between allowed atomic states can be absorbed or emitted from an atom. 36

  37. Hydrogen Spectrum • Transitions from excited state to ground state will emit ultraviolet light. • Transitions from higher excited state to first excited state emit visible photons. 37

  38. Figure 2.19Atomic Excitation 38

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  43. Figure 2.20Helium and Carbon • Allowed energy levels are much more complex when multiple electrons are involved. • Allowed energy levels are much more complex when multiple nuclei are involved (molecules). 43

  44. Figure 2.21Hydrogen Spectra - molecular and atomic Atomic spectrum shows the Balmer lines (the “H” lines) - Ha, Hb, Hg, etc. 44

  45. Review Questions 45

  46. The biggest contributors to global warming are: A) Water vapor and carbon dioxide B) Methane and carbon monoxide C) Chlorofluorocarbons (CFCs), which destroy the ozone layer D) Argon and Helium E) Al Gore and Rush Limbaugh 46

  47. The biggest contributors to global warming are: A) Water vapor and carbon dioxide B) Methane and carbon monoxide C) Chlorofluorocarbons (CFCs), which destroy the ozone layer D) Argon and Helium E) Al Gore and Rush Limbaugh 47

  48. Which is correct A) wavelength * frequency = period B) wavelength * velocity = frequency C) wavelength / velocity = frequency D) wavelength / velocity = period 48

  49. Which is correct A) wavelength * frequency = period B) wavelength * velocity = frequency C) wavelength / velocity = frequency D) wavelength / velocity = period 49

  50. Which list is in the correct order of electromagnetic radiation wavelength, going from shortest to longest? A) infrared, ultraviolet, gamma, radio B) gamma, x-ray, ultraviolet, visible C) radio, infrared, visible, ultraviolet D) radio, x-ray, ultraviolet, visible E) red, violet, blue, green 50

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