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# The Doppler Effect

Physics Talk given on The Doppler Effect lab. Presentation was made to Physics department faculty and students.

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### The Doppler Effect

1. 1. The Doppler Effect Tyler Cash
2. 2. Theory <ul><li>The Doppler Effect – As the source or detector moves in relation to the other, the wavelength gets shorter or longer </li></ul><ul><li> c/f </li></ul><ul><li>Since the speed of light (c) is constant, the frequency must change. </li></ul>
3. 3. Purpose <ul><li>To investigate The Doppler Effect, mainly measuring the frequency of the shifted light and the velocity of the reflector and comparing it to the equation: </li></ul><ul><li>f = 2v/  </li></ul>
4. 4. Apparatus
5. 5. Procedure <ul><li>Measured velocity of reflector for various computer speeds </li></ul><ul><li>(error in time measurement and distance measurement) </li></ul><ul><li>Calculated ratio of actual velocity to computer velocity </li></ul>
6. 7. Velocity Ratio <ul><li>0.36 ± .006 </li></ul><ul><li>This ratio was used to calculate the actual speed in all the following trials </li></ul>
7. 8. Procedure <ul><li>Used the Oscilloscope to measure the frequency of the beam from the moving reflector </li></ul><ul><li>(error in measurement of where the peaks were) </li></ul><ul><li>We then plotted the frequency vs. the velocity of the reflector. </li></ul>
8. 10. Results <ul><li>The slope of our line was </li></ul><ul><li>35.31 kHz/(cm/s) ± .30 kHz/(cm/s) </li></ul><ul><li>We then compared this to the formula </li></ul><ul><li>f = 2v/  </li></ul><ul><li>So our slope should be equal to 2/  </li></ul>
9. 11. Results <ul><li>The wavelength of the He-Ne Laser is </li></ul><ul><ul><li>632.8 nm </li></ul></ul><ul><ul><li>2 . = 3.16 nm -1 </li></ul></ul><ul><ul><li>632.8 nm </li></ul></ul>
10. 12. Results <ul><li>Comparing our slope to this value: </li></ul><ul><li>Slope: 3.53 nm -1 ± .03 nm -1 </li></ul><ul><li>Expected: 3.16 nm -1 </li></ul><ul><li>Value </li></ul>
11. 13. Results <ul><li>Our value did not agree within experimental uncertainty. </li></ul><ul><li>This was somewhat expected because there were some sources of uncertainty we did not account for. </li></ul><ul><li>For Example: Oscilloscope, Vibration of Reflector, Alignment of Laser, Inconsistencies in the String </li></ul>
12. 14. Conclusion <ul><li>Our data was consistent with the theory that as the velocity of the detector increases, the frequency increases. </li></ul><ul><li>Our value for 2/  was not within experimental uncertainty, but was reasonably close considering the error that was unaccounted for. </li></ul>
13. 15. Conclusion <ul><li>We learned that The Doppler Effect applies to light as well as sound. </li></ul><ul><li>Using this information, scientists have been able to discover that the universe is expanding. (The light received from distant stars is red shifted, i.e. longer wavelength) </li></ul>

Apr. 5, 2016
• #### joniebee

Dec. 16, 2015
• #### farooqsabir2505

Apr. 15, 2015

Physics Talk given on The Doppler Effect lab. Presentation was made to Physics department faculty and students.

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