This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Announcements Reading for Wednesday: Review Ch. 4 Online questionnaire due next Wednesday (see assignment section on the web) Exam 1 Last class we did the PE effect http://phet.colorado.edu/simulations/photoelectric/photoelectric.jnlp 0 Battery Voltage Current and we found this V-I curve reverse V, no electrons flow. Looks kind off what we expected when we heat the metal Can we explain the PE effect with classical EM theory? (Is it a heating effect?) Electrons PE effect: A classical phenomena? Assume we could treat light as a classical wave. Predict the behavior (assume light puts energy into plate heats plate up get diode current voltage curve.) Takes time to heat up the plate. Light on longer heat more, more e / s Current rises slowly over time. Color light would not matter, only intensity! 0 Voltage Current photoelectric_en.jar Slow increase if thermal effect What did we observe so far? Color does matter! The velocity (and number) of the electrons seems to increase with frequency ( f UV > f blue > f red ) Positive voltages always yield the same current (at fixed color and intensity). Large negative voltages make the current go to zero. We never observe a negative current. If the light would simply heat up the metal, electrons would come out after some delay....
View Full Document