1. Physics research: Interesting questions, Interesting Independent Lab projects Daniel W. Koon Spring 2005

2. Goals of this talk Describe some general subtopics of physics –Solid State physics –Optics Describe some interesting research questions, including my own research Suggest some Independent Lab project ideas

3. Structure of this talk Solid state physics –Research areas –project ideas Optics – Research areas – project ideas Miscellaneous project ideas

4. Solid state physics: charge transport Charge transport: the measurement of resistivity and Hall effect a “cheap sub-atomic microscope” A “cheap sub-atomic microscope”: How so? It’s cheap It explores how the molecules of the material treat their electrons

5. Resistivity,  Resistance, R: measures how an object resists the flow of current Resistivity,  : measures how a material resists the flow of current So, (SAT flashback)  : R = Density : mass  G(size,shape)  R

6. The Hall coefficient: the other charge transport quantity The Lorentz force: Gives rise to a Hall voltage (The Hall effect is the bending of current due to a magnetic field.)

7. Punchline: charge transport as a cheap subatomic microscope Since we can deduce the microscopic quantities by

8. Koon’s solid state interests I. The phenomenology of charge transport measurement: Error analysis: What do you measure when you measure , R H ? Is there a best sample shape?

9. Error analysis: How to do it Using computer to model current flow in the specimen –To compare different geometries –To test effects of thickness Using a discrete-resistor model in the laboratory –To test linearity of the effect

10. Koon’s solid state interests II. Applying charge transport measurement to specific materials: Hydrogen absorption in rare-earth/Pd bilayers Challenges: Rare earths corrode in O 2. Pd overlayer stops corrosion, allows H 2 absorption. Pd is a much better conductor. So, how do you measure the properties of just the RE?

11. Interesting Solid State questions Is the effect of resistive inhomogeneities linear? Is it additive (If I poke twice as big a hole in a film does it produce twice the effect?) Can we simultaneously measure the resistivity and transmittance of a hydriding or corroding film? [How] does the resistivity, Hall coefficient of a material change as it freezes/thaws?

12. Optics: Biomaterials and more Photonic Polar bears? Solar efficient butterflies? Ulexite (“TV rock”) Scarlet macaws

13. The hairs of the polar bear are transparent light pipes that direct ultraviolet light to its skin -- which is guess what color? Black! So what’s white and black and warm all over? A polar bear under the arctic sun. Paul G. Hewitt, Conceptual Physics, 6th Edition, 1989, p. 501

14. “Aristotle maintained that women have fewer teeth than men; although he was twice married, it never occurred to him to verify this statement by examining his wives’ mouths.” Bertrand Russell

15. Optical attenuation spectrum: polar bear hair

16. FOUL(UP): A Fiber-Optic Ursine Link (Universal Prototype) for telecommunications D. W. Koon and C. L. Jahncke, Physics Dept., St. Lawrence University ABSTRACT: We have constructed what we believe is the first prototype of a fiber-optic link to use the hair of an Arctic mammal. The potential advantages of ursine fiber technology over conventional technology are discussed. http:// it.stlawu.edu/~physics/clj/foulup.html

17. Interesting Optics questions Polar bear hairs as optical fibers? [Reid Hutchins ’98] Morpho butterflies: Does iridescence serve as a solar panel or a sunblock? [Andy Crawford ’99] Ulexite (‘TV rock’): Is there cross talk in the “fiber optic” bundles? [Jay O’Brien ’98] The scarlet macaw: Thin-film iridescence, or diffraction grating, or what?

18. Miscellaneous interesting questions: