class16 - Q1 Photons Interested in Teaching Become a...

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The frequency of a beam of light is decreased but the light’s intensity remains unchanged. Which of the following is true? A. There are more photons per second but each photon has less energy. B. There are more photons per second and each photon has Photons Q1 B. There are more photons per second and each photon has more energy. C. There are fewer photons per second and each photon has less energy. D. There are fewer photons per second but each photon has more energy. E. Nothing happens to the photon number because light is a wave. F. I don’t prepare for class. Interested in Teaching? Become a Learning Assistant! When: Wednesday, February 24 th at 6pm. Where UMC RM 235 Get more info about the LA program: Where: RSVP: By February 19 th to Olivia Holzman ( [email protected] ) Online: http://stem.colorado.edu/Apps Today: What happens in the metal when we shine light on it? Let's revisit the PE effect one last time! What actually happens in the metal when a photon strikes? Why do the emitted electrons have Why do the emitted electrons have different velocities/kinetic energies? What determines the work function ‘ Φ ’? What happens in the metal? Kicker analogy: Photon is like a kicker in a pit… Puts in energy. All concentrated on one ball/electron. Blue kicker has a fixed strength. KE = kick energy - mgh Ball emerges with: mgh = energy needed to make it up hill and out. mgh for highest electron analogous to work function. Red kicker (photon) kicks less than blue one. Nothing gets out. ‘Photon’ ‘Electron Fixed kick energy: Top ones get out… …bottom ones don’t. h metal electrons ‘Electron’ For photons: KE = hf - Φ Different metals different ‘pit depths’ h h sodium- easy to kick out platinum, hard to kick out large work function deep pit small work function shallow pit
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PE effect: Apply Conservation of Energy Energy of photon
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This note was uploaded on 08/24/2010 for the course PHYS 2130 taught by Professor Staff during the Spring '08 term at Colorado.

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class16 - Q1 Photons Interested in Teaching Become a...

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