Experiment Procedure 1. First, click on the Reset button in the Doppler Waves Simulation. This should result in an Unshifted Wavelength (a.k.a., source wavelength) of 400 nm, and a relative velocity ( ) of zero. 2. Press the Play button and watch until at least 12 circular wave fronts have emerged from the source. Then press Pause. 3. Click on any of the wave fronts where it crosses the dashed horizontal line. This should show a nonzero value for x in nanometers, above the main box and to the left of center. 4. The space between two adjacent wave fronts is the apparent wavelength. Now, find two wave fronts that are ten wavelengths apart (have ten spaces between them). Measure the x-value for each and enter them (in nm) below. smaller value nm larger value nm 5. Calculate the difference and divide it by ten. Omit any minus sign. (Enter your answer in nm.) nm This confirms that we are able to measure the unshifted source wavelength with some precision. Now let's investigate the effect of a substantial motion along the line of sight between the observer and the source. 6. Reset the Doppler Waves Simulation. This time, set the source velocity (- ) slider to -0.047. (If you have trouble hitting this number with your mouse or touchpad, click on the dot in the slider. You then can move the slider left and right with your keyboard's left and right arrow keys.) 7. Press the Play button and watch until at least 10 circular wave fronts have emerged from the source. Press Pause. Find two wave fronts that are ten wavelengths apart (have ten spaces between them). Measure the x-value for each, calculate the difference, and divide it by ten. Omit any minus sign. (Enter your answer in nm.) da = nm 8. Is this apparent wavelength greater than, or less than, the source wavelength? O greater than O less than