1. A general expression for a sinusoidal wave is y(x,t) = y_m sin(kx ± w t).  If a wave is moving to the right (toward positive x), which sign (+ or –) should be used in the above expression?  Explain your answer.  

2. Which (if any) of the following parameters of the above wave will change as the wave moves:  amplitude y_m, shape (sinusoidal), wavelength l, or speed v?  

Open and view movie Wave.mov in VideoPoint, as follows.  Go to the course web page, then to  “class activities”, scroll to the bottom and double click on the file.  If the file opens in quicktime, rather than VideoPoint, save the file on your computer and reopen it VideoPoint.  If you don’t have VideoPoint loaded on your computer from last semester, ask your Professor for a CD containing the software.

3. Click on OK to indicate that 1 object will be tracked.  Play the movie by clicking on the “Ø” located below the movie to the left of the slider bar.  You can also use the buttons to the right of the slider bar to advance or rewind the movie frame by frame.  Does the amplitude, shape, width or speed of the wave seem to change very much as the wave propagates (moves)?

·      Calibrate Video Point so that it knows the scale of the graph, by following these steps: 

• Click on the 6^th button down the left that looks like a ruler.  When the pop-up box pops up, click on Continue, leaving 1.00 m as the known length. 
• Next click on the y-axis at the 1 meter mark.  That point will now be marked Scale 1A. 
• Then click directly below that mark on the y-axis at the x-axis (0 meter).  That point will now be marked Scale 1B.  Take the time to line these marks up carefully, as they will affect the accuracy of your results. 

• Measure how the displacement of the wave changes over time at one fixed location, and produce a graph of y vs. t for a fixed value of x.  To do this, chose a position along the x-axis.  Beginning at the start of the movie, take measurements of the vertical height of the wave as a function of time for this one point.  To do this, click on the top icon on the left side of the screen.  Then place the cursor, which should now look like “location cross-hairs”, over the point you want to record.  Click on the point along the wave at the location you are tracking.  Once you click, the movie frame will advance to the next frame. Repeat this process for at least 30 points, making sure to always be at the same x-value.  The more careful you are lining up the cross-hairs, the better your data will be.

• Display a graph of y vs. t for the value of x that you chose. To display a graph of the y vs. t, click on the 8^th icon down on the left.  This icon shows two axes and a few data points (i.e.it looks like a graph).  Change the x to y in the Vertical Axis box, then select Position and click OK. Display the graph along side one frame of the movie.

4. What is graphed in one frame of the movie?  Is it y vs. t, y vs. x or something else? 

5. From which figure (the frame of the movie or the graph of y vs. t) would you gather information about the wavelength of the wave? 
   
   
6. From which figure (the frame of the movie or the graph of y vs. t) would you gather information about the period of the wave? 

7. Find each of the following parameters of the wave:  wavelength, wavenumber, period, wave speed, frequency, angular frequency, amplitude

8. Write the complete mathematical expression for this wave, using the numbers from your data in the place of the corresponding variables. (Hint: y = y_m sin(kx – w t) is the general expression for a wave.)