Doppler Lab

Doppler Lab

Purpose:

In this activity you will be examining how the wave pattern changes as the object creating the waves changes its speed.


Procedure:

  • For this entire lab you will be using the program found here.
  • Part 1:  Subsonic Speeds

    1. In this part of the lab you will be looking at the wave patterns around objects that are traveling slower than the waves travel.

    2. Begin with the frequency set on 1.0, the wave speed set on 100 and the object speed set on 0.

    3. Start the program and allow your object to make a few waves.  Pause the program and measure the wavelength of the waves both in front of and in back of the plane.  Use these wavelengths and the speed of the waves to calculate the frequency of the waves (frequency = velocity of waves/wavelength of waves)

    4. Record your information in a data table similar to the one shown below.


    5. End this trial and set your object speed to 10 m/s.  Start the plane moving across the sky and when it has just passed the halfway point, collect all your data again.

    6. Continue this procedure increasing your speed by 10 m/s for each new trial until you have reached 90 m/s.  Do not try to collect data yet for 100 m/s. 

    7. Temporarily set your object speed back to 70 m/s.  Allow the plane to travel about 70 percent of the way across the screen and the pause your simulation.  Carefully sketch the plane and its wave pattern into your lab book for this speed.

    8. Answer the questions found here.

    Part 2:  Sonic Speeds

    1. In this part of the lab you will be looking at the wave patterns around objects that are traveling at the same speed that the waves travel.

    2. Begin with the frequency set on 1.0, the wave speed set on 100 and the object speed set on 100.

    3. Start the plane moving across the screen and notice the pattern in front of the plane. Pause your simulation when the plane has progress about 75% of the way across the screen.  Draw this pattern into your lab book .  Measure the wavelength and frequency behind the plane.  Include these numbers in your drawing.

    Part 3:  Supersonic Speeds

    1. In this part of the lab you will be looking at the wave patterns around objects that are traveling at speeds greater than the waves travel.

    2. Begin with the frequency set on 4.0, the wave speed set on 50 and the object speed set on 50.

    3. Start the plane moving across the screen and notice the pattern in front of the plane.  You don't need to write anything down at this point but keep a mental note of what the pattern looks like.

    4. Increase the speed of the plane to 60 m/s and allow it to move about 75% of the way across the screen.  Pause the simulation and make a sketch of the plane and the waves in your lab book.  Label this drawing as slightly supersonic.

    5. Increase the speed by 10 m/s at a time and observe the pattern formed by the waves.  You don't need to record anything for these trials.

    6. When you hit 100 m/s (2x the speed of sound) again draw a sketch of the wave pattern when the plane has reached the 75% mark.  Label this picture as super super sonic.

    7. Answer the questions found here.



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