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

2. Exam 1 Results

5. Electromagnetic radiation / wave More like waves More like particles Wavelength (meters) Frequency (Hz) Temperature required to glow this color

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)

10. Cosmic Background Microwave Radiation Universe Opaque Universe Transparent

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. 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. 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

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. “ 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. 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