PHY 1033 Fall 2011 Exam #3 In class (1 hr. 40 min. ending 4:40 pm) Ihas Nov. 1 You are allowed to consult one 8.5”x11” sheet of paper with anything written on it in your own hand, and to use a calculator, ruler, and pencils or pens. Do not violate the UF honor code. Turn off cell phones or put in aircraft mode. Answers without the required justification or explanations will be counted wrong, even if they are correct. You may quietly ask me any question after raising your hand, but my answers will only clarify the exam questions. Good luck! c(light in air) = 3x108 m/s h = 6.6x10‐34 J/Hz Q(electron) = 1.6x10‐19 Coulombs c(sound in classroom air) = 341 m/s n(water) = 1.33 n(diamond)=2.4 1. What are the fields and their relative orientation that compose a light wave? 2. What is physically required for an induced magnetic field to produce an electric current? 3. A positively charged particle in front of you moves directly away from you. There is a vertical magnetic field present. In what direction, relative to you, is the force on the particle from the magnetic field? 4. You hold your right arm straight up over your head during a thunder storm. Lightning strikes your right hand, which causes a flow on electrons through your arm toward the ground. Use your right hand rule to determine what the magnetic field looks like produced in the vicinity of your right arm and draw a picture (show flux direction). 5. The figure shows a situation involving Faraday’s Law. If we move our hand AWAY from the coil of wire (moving to the right‐red arrow flipped around), what else, if anything, will change in the picture and why? 6. What is Brewster’s angle (in degrees) for light reflecting off a facet of a diamond?° 7. Which pole of the Earth’s magnet is near the south geographic pole? 8. You rub a plastic straw, electrically charging it, and run with it in a straight line at a constant speed of 3 m/s. . What is the frequency of E‐M radiation produced? 9. Visible light is impinges on the window of a microwave oven, which is running at 2.45 gigahertz (GHz). In what part of the E‐M spectrum is the radiation after it is reflected from the window? 10. Light with frequency f=2x1015 Hz strikes a metal, releasing an electron with zero speed (no kinetic energy). What is the work function of the metal surface? 11. What is the wavelength of the photon in the problem above? Show you equations. 12. What part of the E‐M spectrum is the photon in the problem above? Show your logic. 13. What would be the kinetic energy of the electron ejected in problem #10 if the photon has a frequency f=4x1015 Hz ? 14. Sketch the magnetic lines of flux for 2 bar magnets placed along a line with their north poles facing each other and a gap equal to 1/3 the length of each magnet between them. Put in arrow heads to show the direction of the flux. 15. .Sketch the magnetic lines of flux for 2 bar magnets placed along a line with the north pole of one facing the south pole of the other and a gap equal to 1/3 the length of each magnet between them. Put in arrow heads to show the direction of the flux. 16. Describe one modern device in everyday use which employs Lenz’s Law and/or the law of induction (Faraday’s Law). If you cannot describe such a device, then state Lenz’s Law. 17. (4 pts) You take the following data on the photo‐electric effect: V = 2.1 volts λ = 500 nm V = 1.7 volts λ = 550 nm V = 1.1 volts λ = 800 nm V = 0.8 volts λ = 950 nm Make a neat graph of E(electron) vs. f(photon). Use your ruler to get the scales correct, in Joules (y‐axis) and Hz (x‐axis). Extra credit (2 pts): What is the slope (TO AT LEAST 2 FIGURES) of the best straight–line fit to the plotted points in units of Joule‐sec?