1. Charles Hakes
Fort Lewis College 1

2. Chapter 2
Spectroscopy /
Review
Charles Hakes
Fort Lewis College 2

3. Outline Test Wednesday Spectroscopy Check posted grades! Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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)
Charles Hakes
Fort Lewis College 7

8. Test Topics Chapter 5 - Earth and Moon Chapter 6 - Terrestrial Planets
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
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 9

10. Figure 2.10 Blackbody Curves
Note the logarithmic temperature scale.
For linear scale, go look at the “black body” section of:
example - oven
Charles Hakes
Fort Lewis College 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)
Charles Hakes
Fort Lewis College 11

12. Small Group Exercise recall: F = sT4
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
Charles Hakes
Fort Lewis College 12

13. When it is hottest, each m2 of surface radiates how much more energy?
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
Charles Hakes
Fort Lewis College 13

14. When it is hottest, each m2 of surface radiates how much more energy?
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
Charles Hakes
Fort Lewis College 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?
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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)
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 20

21. Spectroscopy
Charles Hakes
Fort Lewis College 21

22. ROY G BIV
Charles Hakes
Fort Lewis College 22

23. ROY G BIV red orange yellow green blue indigo violet Charles Hakes
Fort Lewis College 23

24. Figure 2.11 Spectroscope
Charles Hakes
Fort Lewis College 24

25. Figure 2.12 Emission Spectrum
Charles Hakes
Fort Lewis College 25

26. Figure 2.15 Absorption Spectrum
Charles Hakes
Fort Lewis College 26

27. Figure 2.16 Kirchhoff’s Laws
Charles Hakes
Fort Lewis College 27

28. Figure 2.13 Elemental Emission
Charles Hakes
Fort Lewis College 28

29. Figure 2.14 Solar Spectrum
Charles Hakes
Fort Lewis College 29

30. But where do those lines come from?
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 31

32. Quantum Mechanics (How to build an atom)
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 34

35. Figure 2.18 Modern Atom - note electron “cloud”
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 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.
Charles Hakes
Fort Lewis College 37

38. Figure 2.19 Atomic Excitation
Charles Hakes
Fort Lewis College 38

39. Charles Hakes
Fort Lewis College 39

40. Charles Hakes
Fort Lewis College 40

41. Charles Hakes
Fort Lewis College 41

42. Charles Hakes
Fort Lewis College 42

43. Figure 2.20 Helium 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).
Charles Hakes
Fort Lewis College 43

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

45. Review Questions
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 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
Charles Hakes
Fort Lewis College 47

48. Which is correct A) wavelength * frequency = period
B) wavelength * velocity = frequency
C) wavelength / velocity = frequency
D) wavelength / velocity = period
Charles Hakes
Fort Lewis College 48

49. Which is correct A) wavelength * frequency = period
B) wavelength * velocity = frequency
C) wavelength / velocity = frequency
D) wavelength / velocity = period
Charles Hakes
Fort Lewis College 49

50. A) infrared, ultraviolet, gamma, radio
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
Charles Hakes
Fort Lewis College 50

51. A) infrared, ultraviolet, gamma, radio
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
Charles Hakes
Fort Lewis College 51

52. Three Minute Paper Write 1-3 sentences.
What was the most important thing you learned today?
What questions do you still have about today’s topics?
Charles Hakes
Fort Lewis College 52