ASSIG12 - Section: _ Name: _ Assignment 12: Quantum Physics...

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Section: ______ Name: ______________________________ Section Instructor: ______________________________ Physics 2208, Spring 2009 1 Cornell University Assignment 12: Quantum Physics II Concepts: laser wave aspects of particles de Broglie wavelength ( λ = h p ) diffraction of electrons & other particles electron microscope Schrodinger’s equation wave functions & probability density quantization & standing waves tunneling LEDs & solar cells Reading in text: Chapter 38: Sections 5-7. Optional: Sections 8, 9. Chapter 39: Sections 1-9. Chapter 40: Sections 1-3, 7, 8, 11, 12. Chapter 41: Optional: Section 10. Reading in lab manual: Unit 12 Supplement: Devices Using p-n Junctions—LEDs and Solar Cells. Some possibly useful values: Description Symbol & Value speed of light c = × = × 300 10 81 .. m/s nm/s 7 Planck constant h = × × 6 63 10 414 10 34 15 .J s = . e V s hc hc = × 1240 10 3 .e V n m elementary charge e = × 160 10 19 .C electron mass mc e kg MeV = × = 911 10 0511 31 2 proton mass p kg MeV = × = 167 10 938 27 2 . neutron mass n kg MeV = × = 168 10 940 27 2 . Assignment: No quiz on Assignment 12. Due in lecture on Monday April 27. 1. A semiconductor diode laser (like the ones you’ve been using in the Physics 2208 lab) has a power output of 3.0 mW and a wavelength of 670 nm. The diameter of the laser beam as it exits the laser is about 1 mm. (a) What is the average intensity of this laser beam? How does this intensity compare with the intensity of bright sunlight (about 1000 ) and the intensity of radiation at a distance of 10 cm from a 100 W lightbulb? 2 W/m (b) How many photons/s are produced by this laser? (c) The spreading or divergence of this laser beam can be estimated by assuming that it is diffraction-limited , i.e., that the beam spreads like the central bright spot in a diffraction pattern from a circular aperture whose width is the beam’s initial width. What is the divergence angle (full-angle width) of this laser beam, assuming it is circular in cross- section?
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ASSIG12 - Section: _ Name: _ Assignment 12: Quantum Physics...

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