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Unformatted text preview: 12/29/04 1 Activity 2 Solutions: Electromagnetic Waves – Radiant Energy I 2.1 How Do Electromagnetic Waves and Other Waves Transmit Energy? Your instructor will discuss the properties of waves. 1) Transferring energy with waves a) Stretch a slinky along the length of your table with a student holding each end. Vibrate one end of the slinky to send sine waves along it. What can you do to increase the frequency of the waves? Vibrating the slinky faster increases the frequency of the waves (how often one of the wave crests passes a given point on the table). b) What does increasing the frequency of the waves do to the wavelength? The wavelength becomes shorter. c) Place a Styrofoam ball near the slinky. Send one pulse wave along the slinky to knock the ball off of the table. Is it possible to transfer energy without a transfer of matter? Some of the energy of the wave is converted into the kinetic energy of the ball. This is an example of transferring energy with no transfer of matter (no matter was transferred down the slinky, and no matter was transferred to the ball). d) Group Discussion Question: List examples of transfer of energy without a transfer of matter. 2) Wave Speed and Frequency Your instructor will discuss wave periods and frequencies. Use this information to find the speed of the wave illustrated in the diagrams below. a) Find the wavelength (in meters) of the wave in the diagram. 3 cm = 0.03 m Distance (in cm) Displacement 1 2 3 4 5 6 10 9 8 7 12/29/04 2 b) The diagram below shows the displacement of a wave over time, at a fixed point along the path of the wave. Find the period of the wave in the diagram. _ 1.5 seconds_ c) Calculate the frequency of the wave (in cycles/second, or Hertz). frequency = 1/period = 1/1.5 sec = 0.67 cycles/sec = 0.67 Hz d) Calculate the speed of this wave. S = f L = 0.67 Hz x 0.03 m = 0.02 m/s = 2 x 10 – 2 m/s e) Based on the speed you calculated, could these diagrams represent a wave of electromagnetic radiation? Why or why not? This could not be a wave of electromagnetic radiation because it is traveling too slowly. All waves of electromagnetic radiation travel at the speed of 3 x 10 8 m/s (in a vacuum). When traveling in other media, such as air or water, the speed of electromagnetic waves is only slightly slower....
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This note was uploaded on 06/11/2011 for the course PHYSICS 104 taught by Professor Staff during the Winter '11 term at Ohio State.
- Winter '11