Physics research: Interesting questions, Interesting Independent Lab projects

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, r • Resistance, R: measures how an object resists the flow of current • Resistivity, r : measures how a material resists the flow of current • So, (SAT flashback) • r : 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, RH? • 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 O2. • Pd overlayer stops corrosion, allows H2 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 telecommunicationsD. 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: