08 Feb 17 Light, Electron E Levels Actual Presented

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Introduction to electromagnetic radiation and light. Viewing atomic spectra with diffraction gratings. Optical tweezers (cool example of light having momentum).

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08 Feb 17 Light, Electron E Levels Actual Presented

  1. 1. Today: Electromagnetic Radiation; Light & Sources of Light; Atomic spectra <ul><li>Optical tweezers study of RNA polymerase </li></ul>Steve Block Lab, Stanford
  2. 2. Exam 1 Results
  3. 3. Electromagnetic radiation / wave <ul><ul><li>Carries energy </li></ul></ul><ul><ul><li>Has momentum (oomph) (but does NOT have mass) </li></ul></ul><ul><ul><li>In a vacuum travels at “light speed” (duh?) </li></ul></ul><ul><ul><li>Behaves like particle AND wave (what the???) </li></ul></ul><ul><ul><li>Oscillating Electric and Magnetic “Field” </li></ul></ul>
  4. 4. Electromagnetic spectrum <ul><ul><li>Carries energy </li></ul></ul><ul><ul><li>Has momentum (oomph) (but does NOT have mass) </li></ul></ul><ul><ul><li>In a vacuum travels at “light speed” (duh?) </li></ul></ul><ul><ul><li>Behaves like particle AND wave (what the???) </li></ul></ul><ul><ul><li>Oscillating Electric and Magnetic “Field” </li></ul></ul>Wavelength (meters) Frequency (Hz) Temperature required to glow this color
  5. 5. Electromagnetic radiation / wave More like waves More like particles Wavelength (meters) Frequency (Hz) Temperature required to glow this color
  6. 6. Clicker Question—Electromagnetic Waves, Frequency <ul><li>Which of these EM waves has the highest frequency </li></ul><ul><li>Radiowave </li></ul><ul><li>Ultraviolet </li></ul><ul><li>Visible red light </li></ul><ul><li>Microwave </li></ul>
  7. 7. Clicker Question—Electromagnetic Waves, Frequency <ul><li>Which of these EM waves has the highest frequency </li></ul><ul><li>Radiowave </li></ul><ul><li>Ultraviolet </li></ul><ul><li>Visible red light </li></ul><ul><li>Microwave </li></ul>
  8. 8. What are sources of electromagnetic radiation (EM)? Sunshine … fusion / atoms? Core of Earth (Earth’s magnetism) Microwave (oven/sure) …. Electrons Cell phones (microwaves) … electrons are oscillating Radio waves … antennaes … metal electricity / electrons Gamma rays … from pulsars (could be proton / neutrons) Infrared and light waves from an explosion (lots of different electron thing)
  9. 9. You are always basking in a glow of EM radiation! <ul><li>EM Waves are everywhere, always </li></ul><ul><ul><li>Even in the “dark” or in “space” </li></ul></ul><ul><li>Because you are at 310 Kelvin (98.6 degrees), </li></ul><ul><li>you emit radiation yourself! </li></ul>
  10. 10. Cosmic Background Microwave Radiation Universe Opaque Universe Transparent
  11. 11. Visible light is a small portion of the EM spectrum But of course, the most “colorful”! Key concept: Energy of photon is proportional to frequency E = h * f
  12. 12. Models of the atom evolved quickly in the early 1900’s Electron “Shells” Figure 11.6 in texbook http://www.csmate.colostate.edu/cltw/cohortpages/viney/atom2.jpg Electron clouds http://www.youtube.com/watch?v=fKYso97eJs4&feature=related Plum Pudding “ Solar System” model
  13. 13. Atomic spectra http://www.walter-fendt.de/ph11e/bohrh.htm (Standing waves and resonance for Bohr model) http://www.lon-capa.org/~mmp/kap29/Bohr/app.htm http://www.youtube.com/watch?v=l4yg4HTm3uk Spectrum of the stars
  14. 14. <ul><ul><li>A) Each type of gas has a different molecular weight, which causes the nucleus to have different possible energy levels </li></ul></ul><ul><ul><li>B) Each type of gas has a different orbital structure, which leads to different possible electron energy differences in the emission lines </li></ul></ul>What causes the emission lines of various gases to differ in color?
  15. 15. Laser light can be used to create a real-life “tractor beam” Fictional Tractor Beam Steve Block Lab, Stanford “ Laser Tweezers” for biophysics experiments
  16. 16. “ Laser Tweezers” or “Optical tweezers” have become incredibly powerful tools for biophysics Optical tweezers I built at Cornell (M. Wang lab w/ Richard Yeh)
  17. 17. Here are some actual videos of optical tweezers in action Sorting colored microspheres http://www.ppo.dk/Research-OT.html Fiber optical trap, http://members.yline.com/~tweezers/gallery.htm Kinesin Molecular Motor http://www.scripps.edu/milligan/research/movies/kinesin_mpg.html Steve Block Lab, Stanford
  18. 18. Clicker Question—Light <ul><li>Hopefully you know that light carries energy . But does light carry momentum? </li></ul><ul><li>Yes, always </li></ul><ul><li>Sometimes </li></ul><ul><li>No! Light does NOT have mass! </li></ul>Edned lecture here

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