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The worksheet for the simulation will be in the student’s booklets.

Simulation of “blackbody” is in Phet. The worksheet for the simulation will be in the student’s booklets. Heineman has a greenhouse gas sim. Simulation of microwave oven is in Phet (has to do w why N2 and O2 do not act as greenhouse gases). Ask the candidates:

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The worksheet for the simulation will be in the student’s booklets.

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  1. Simulation of “blackbody” is in Phet The worksheet for the simulation will be in the student’s booklets. • Heineman has a greenhouse gas sim Simulation of microwave oven is in Phet (has to do w why N2 and O2 do not act as greenhouse gases) • Ask the candidates: • Try all of the controls to get a sense of what they do. • How does x affect y? (draw graph) Simulation of greenhouse gases is in Heineman, and probably Phet too

  2. Mr. Klapholz Shaker Heights High School Energy, Power, and Climate Change (8) http://www.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/Mauna_Loa_Carbon_Dioxide-en.svg/800px-Mauna_Loa_Carbon_Dioxide-en.svg.png&imgrefurl=http://commons.wikimedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide-en.svg&usg=__O_oYGV95EgWGRMOCpdngnXQ5gf4=&h=515&w=800&sz=80&hl=en&start=0&zoom=1&tbnid=x8dJZdK33FKBRM:&tbnh=113&tbnw=175&prev=/images%3Fq%3Datmospheric%2Bcarbon%2Bdioxide%2Bmeasured%2Bat%2Bmauna%2Bloa%2Bhawaii%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1280%26bih%3D645%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=286&vpy=185&dur=793&hovh=180&hovw=280&tx=99&ty=81&ei=90gqTaW_MoaKlwfElYXbCw&oei=90gqTaW_MoaKlwfElYXbCw&esq=1&page=1&ndsp=18&ved=1t:429,r:1,s:0

  3. How does a greenhouse work? http://blog.makezine.com/archive/2009/03/greenhouse_from_old_windows.html

  4. Why do cars get so hot in the summertime?(And why doesn’t the color of the paint matter?) http://www.google.com/imgres?imgurl=http://www.ctrade.com.au/Portals/0/Car-Greenhouse2.jpg&imgrefurl=http://www.ctrade.com.au/LocalPower/Schools/Learn/TheGreenhouseEffect/tabid/104/Default.aspx&usg=__Uay5FfvdDk9maDN56EHngl7foqA=&h=317&w=400&sz=38&hl=en&start=0&zoom=1&tbnid=06EKtbTgmB_06M:&tbnh=124&tbnw=156&prev=/images%3Fq%3Dgreenhouse%2Bcar%2Bwindow%26um%3D1%26hl%3Den%26biw%3D1280%26bih%3D645%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=128&vpy=181&dur=484&hovh=124&hovw=156&tx=116&ty=73&ei=ioAqTefJOoTGlQenxNjbAQ&oei=cIAqTfzfO8WAlAfUsODHCw&esq=4&page=1&ndsp=18&ved=1t:429,r:0,s:0

  5. Intro to the Greenhouse effect “The ability of the atmosphere to capture and recycle energy emitted by the Earth surface is the defining characteristic of the greenhouse effect.” http://en.wikipedia.org/wiki/Greenhouse_effect

  6. Greenhouse Effect in brief The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere. As a result, the temperature there is higher than it would be if direct heating by solar radiation were the only warming mechanism.

  7. Details of the greenhouse effect Understanding this effect gives us the opportunity to apply a lot of the physics that we have studied this year (and even a bit more).

  8. Remember Electron Orbits http://wisp.physics.wisc.edu/astro104/lecture6/lec6_print.html

  9. These Electron Transitions Emit Light http://www.files.chem.vt.edu/RVGS/ACT/notes/notes-electronic_structure.html

  10. Atoms and Light • Why do atoms only absorb photons of specific frequencies? • Why do atoms emit the same frequencies that they absorb?

  11. Ionization of Atoms • What is an ion? • If a photon has enough energy, then it will knock an electron off of an atom. • The energy (E = hf) does not need to be the same as the transition between energy levels.

  12. Molecules http://www.erichufschmid.net/Global-warming/Global-warming.html

  13. Molecules can do things that atoms can’t. http://www.phy.davidson.edu/stuhome/derekk/resonance/pages/co2.htm

  14. Molecules, Energy, and Light • Molecules can absorb light in the same way that atoms can absorb light, and in a different way too. • Molecules can do things that atoms cannot do: rotate (spin), vibrate (compress and extend), bend, … • Molecules can absorb photons that have energies that resonate with all the things that they can do. These photons all are lower energy (frequency) than electron transitions. These photons are in the infrared (“heat”) part of the E-M spectrum.

  15. Atoms, Molecules, Gases, Liquids, Solids • As we consider systems with more particles, and as those particles get closer together, the systems are better at absorbing photons. • When light hits the surface of the earth, it is usually absorbed.

  16. Albedo http://www.the-m-factory.com/portfolio/illustrated/illustrated_08.html

  17. Albedo • Albedo = reflected radiation / absorbed radiation • Snow Albedo = 90 % • Forest Albedo = 10 % • Average for Earth: 30 %

  18. Blackbody Radiation • Everything glows to some degree. • Solids emit a lot of frequencies, but not all frequencies are equally intense. • Analyzing the light tells you the temperature of the body. http://quantumfreak.com/introduction-to-blackbody-radiation/

  19. Blackbody Radiation • The greater the temperature, the more light is emitted. • The greater the temperature, the higher the frequency of the most intense light. • The greater T, the less l. http://schools-wikipedia.org/wp/t/Thermodynamic_temperature.htm

  20. Blackbody Radiation http://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/chap18/F18-02%20Planck%20black%20body.jpg

  21. Blackbody Radiation • Notice where the red is. • At room temperature, bodies emit mostly in the infrared. • The sun is so hot that it emits in the visible range. • Why do animals see so well in the range where the sun emits light? http://www.egglescliffe.org.uk/physics/astronomy/blackbody/bbody.html

  22. Wein’s displacement law lmax = B / T B = 2.89 x 10-3m K

  23. Problem Approximately what is the temperature of an object that radiates most of its energy as yellow light?

  24. Solution Yellow light has a wavelength of about 570 nm. 570 nm = 570 x 10-9m lmax = B / T lmax = 2.89 X 10-3m K / T T = 2.89 X 10-3m K / lmax T = 2.89 X 10-3m K / 570 x 10-9m T ≈ 5000 K ( This is approximately the temperature of the surface of the sun. )

  25. “Infrared” vs. “Heat” All objects radiate electromagnetic energy. When it’s in the visible range for humans, we call it “light”, but it is light no matter what the frequency. Objects at room temperature emit almost no light that we can see, but they do emit plenty of light in the ‘infrared’ region. Since hotter objects emit more infrared light than cooler objects, we sometimes call infrared light “heat”, but it is not heat, it is just light that comes from hot objects. Please see the next slide…

  26. \ http://www.kollewin.com/blog/electromagnetic-spectrum/

  27. Stefan-Boltzmann Law • The hotter the object, the greater the intensity of radiation that is emitted: • Power per unit area = sT4 • s = 5.67 x 10-8 W m-2 K-4

  28. Problem Light from the sun is most intense around the color blue. What temperature is the surface of the sun?

  29. Solution From , lmax = 2.89 x 10-3m K / T T = 2.89 x 10-3m K / lmax Blue light has a wavelength of about 420 nm. So T = 2.89 x 10-3m K / (420 x 10-9m) T = 6900 K

  30. The earth absorbs the sun’s light… The earth is getting a lot of energy every second. Why doesn’t the earth get hotter and hotter? Tell your buddy. The earth radiates energy back into space… If the earth radiated less than it does, then the earth would cool. If the earth radiated more than it does, then the earth would warm. The earth radiates energy at the same rate that the earth absorbs energy.

  31. What if you put a very cold earth in our place? At first the earth would radiate very little energy. As the earth warmed up, the earth would radiate more and more. At equilibrium, the earth would radiate as much as it received.

  32. Our first climate calculation If the earth had no atmosphere, then the energy coming in from the sun would balance the energy it radiated out. What would be the average temperature of the earth? Givens: Solar constant: 1380 W m-2 Radius of earth = 6.4 x 106m (Value to check at the end: Average temperature of the earth is 59˚F = 15˚C = 288 K)

  33. Solution (1 of 5) • Since the temperature of the earth is steady, the energy arriving equals the energy leaving. • The energy arriving is from the sun. • The energy leaving is by radiation.

  34. Solution (2 of 5) • The energy arriving is from the sun. The product of the solar constant and area gives the power (energy per second). Rate of energy arriving = {1380 W m-2}×{Area} • Which area should we use? …

  35. The area receiving the radiation is equivalent to a disc. http://www.google.com/imgres?imgurl=http://i27.photobucket.com/albums/c153/Borodog/NotFlat.png&imgrefurl=http://forumserver.twoplustwo.com/47/science-math-philosophy/why-does-moon-look-flat-275840/index8.html&usg=__sF-v6TGyMHAjoVxL2QzzQrRZ9XM=&h=525&w=800&sz=230&hl=en&start=0&zoom=1&tbnid=FCaJLXNp2y00TM:&tbnh=169&tbnw=268&ei=ArEwTeyMKIL-8Abwi5nqCA&prev=/images%3Fq%3Dsphere%2Blooks%2Blike%2Bdisc%26um%3D1%26hl%3Den%26biw%3D1280%26bih%3D645%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=164&vpy=276&dur=705&hovh=182&hovw=277&tx=109&ty=102&oei=eLAwTe2cLIGEswbEmfiICg&esq=5&page=1&ndsp=15&ved=1t:429,r:5,s:0

  36. Solution (2 of 5) • The energy arriving is from the sun. The product of the solar constant and area gives the power (energy per second). Rate of energy arriving = {1380 W m-2}×{Area} • Which area should we use? • Area of a disc = pR2 Power arriving = {1380 W m-2}×{p(6.4 x 106 m)2} Power arriving = 1.75 x 1017 W

  37. Solution (3 of 5) • Energy arrives from the sun at 1.75 x 1017 W. • But a portion of it goes right back out into space, due to reflection. The reflected portion does not contribute to the energy balance on earth. • The average albedoof the earth is 30 % = 0.30 • So 70 % of the energy from the sun does enter our energy balance. • 0.70 x 1.75 x 1017 W = 1.23 x 1017 W {  } • This is the relevant value of solar energy that arrives at earth.

  38. Solution (4 of 5) • The energy leaving is by radiation. • Use the Stefan-Boltzmann law: Rate of energy leaving per area= sT4 Rate of energy leaving = Area×s×T4 • Which area should we use? • Over what area does the earth radiate? • Area of a sphere = 4pR2 Rate of energy leaving = (4pR2)×s×T4 Power leaving =4p(6.4x106m)2(5.67x10-8Wm-2K-4)×T4

  39. Solution (5 of 5) Power arriving = Power leaving 1.23x1017W = 4p(6.4x106m)2(5.67x10-8Wm-2K-4)×T4 Solve for Temperature T = 255 K = -18˚C = 1˚F This is colder than the average temperature of the earth (288 K), but we left out the earth’s atmosphere. We left out the (natural) greenhouse effect.

  40. Emissivity (1 of 4) A big help in getting the energy equation to work out better comes from realizing that the earth does not act like a perfect “blackbody”. Real objects do not act like perfect black bodies; real objects emit less energy than a perfect black body would at the same temperature. Because the atmosphere acts like a blanket, the earth radiates energy at a rate less than sT4.

  41. Emissivity (2 of 4) Emissivity is a unitless number that describes how it resembles a perfect black body. Emissivity is calculated by dividing the real output of the object by the perfect blackbody output. A dull, black lump of rock has an emissivity of about 0.9 A mirror has an emissivity of about 0.1

  42. Emissivity (3 of 4) If the earth did radiate like a perfect blackbody, then it would radiate at this rate: Power Leaving = (Area of sphere)×sT4 Power Leaving = [4p(6.4x106)2]×(5.67x10-8)×(288)4 Power Leaving = 2.0 x 1017 W The real power leaving the earth is the same as the real power arriving at the earth: 1.23 x 1017 W {  } How would you calculate the emissivity of the earth?

  43. Emissivity (4 of 4) The emissivity of the earth is: e = { 1.23 x 1017 W } ÷ { 2.0 x 1017 W } e = 0.6

  44. The role of the atmosphere in climate • Every molecule can absorb radiation, and when it does, it often emits that same frequency, but in a random direction. • Our atmosphere has an upper layer with ozone (O3) and a lower layer with water vapor and carbon dioxide (CO2)

  45. Ozone (O3) is one of the forms of oxygen. Recall what is meant by an “absorption spectrum” https://www.windows2universe.org/physical_science/chemistry/oxygen_ozone.html&edu=elem

  46. Recall what is meant by an “absorption spectrum” Hydrogen Hydrogen Why are only specific colors emitted / absorbed by hydrogen? Hydrogen Hydrogen How do the emitted colors relate to the absorbed colors? http://www.cbu.edu/~jvarrian/252/emspex.html

  47. Absorption Spectra(for the moment, just read everything on the graph). http://chriscolose.wordpress.com/2008/03/09/physics-of-the-greenhouse-effect-pt-1/

  48. Absorption Spectra. Notice that the atmosphere does not absorb visible light! http://chriscolose.wordpress.com/2008/03/09/physics-of-the-greenhouse-effect-pt-1/

  49. Absorption Spectra. Ozone absorbs UV light, making life possible on earth! http://chriscolose.wordpress.com/2008/03/09/physics-of-the-greenhouse-effect-pt-1/

  50. Greenhouse gases are transparent to incoming solar radiation…

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