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EC Finding the Speed of Light with Marshmallows

EC Finding the Speed of Light with Marshmallows - 4 Remove...

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Extra Credit: Finding the Speed of Light with Marshmallows PHYS 1402 Name _________________________ A microwave oven generates electromagnetic waves that have wavelengths on the order of a few centimeters. These microwaves are reflected on the inner walls of the oven and interfere with each other to produce areas of maximum amplitude and areas of minimum amplitude. The result is that the microwave oven does not cook evenly and hot spots are formed. (This is the reason that turn-tables are used.) Equipment Needed: Microwave oven, Metric Ruler, marshmallows, and a microwave-safe casserole dish (8 x 11.5 or 10 x 15)(inches) Procedure: 1. Fill a microwave-safe casserole dish with marshmallows, completely covering it with a layer one marshmallow thick 2. Remove any turn-table from the oven. 3. Put the dish of marshmallows in the microwave and cook on low heat. Microwaves do not cook evenly and the marshmallows will begin to melt at the hottest spots in the microwave. Heat the marshmallows until they begin to melt in four or five different spots.
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Unformatted text preview: 4. Remove the dish from the microwave and observe the melted spots. Take the ruler and measure the distance (D) between the melted spots. (Measure the center-to-center distance between any two nearest neighbors.) Repeat this measurement at least four times. (Choosing two different melted spots each time.) You will find that one distance repeats over and over. This distance will correspond to half the wavelength of the microwave, about 6 cm. D ( ) D ( ) 1 4 2 5 3 6 5. Calculate the average distance between melted spots: D avg = __________ 6. Calculate the average Wavelength: Wavelength avg = __________ 7. Now turn the oven around and look for a small sign that gives you the frequency of the microwave. Most commercial microwaves operate near 2400 MHz. 8. Calculate the speed of light: Velocity = Frequency × Wavelength = ________________ ( The Physics Teacher, vol. 35, April 1997, p. 231. Copyright 1997 American Association of Physics Teachers )...
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