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Photoelectric Vending Machine Nathan Miller Univ. of Wisconsin Eau Claire
Table of Analogies: Money Energy Candy Bars (100 g choc). Electrons Vending Machine Metal Surface Price of Candy Bar ($1) Work Function Change KE of emitted electron
• Basic classical exchange • Money in Chocolate out • A “class” has a certain amount of money, they should be able to buy a certain amount of chocolate
• Say you have class of 100 students, with $65 dollars between them. They should be able to buy 6500 g of chocolate. • But if they each have $0. 65 and each walk by the vending machine, they don’t get a single candy bar. • This is like shining red light on the surface – no matter how much you shine, no electrons is emitted.
• Now say you have a class of 10 students, and each has a dollar. • They can now buy 1000 grams of chocolate in total • This time they can in fact buy the candy bars, but there is no energy left over. • This is like blue light at the critical frequency – electrons are ejected, but no KE is left over.
• Finally, you have 2 people who have $1. 50 each. • They can buy the candy bars, and each has 50 cents left over. • This is like ejecting electrons and giving them a certain amount of kinetic energy.
• If you have a vending machine with 65 cent candy bars or $1. 10 candy bars, these would correspond to different work functions.