Activities

1. With the default values you may see (in the animation and in the graphics) the Doppler effect at work: when source and detector are approaching (moving away) the time interval is shorter (larger) between detections than between emissions, i.e., the detected frequency is higher (lower).
2. Click over the bars corresponding to consecutive emissions (detections) to see the corresponding times. Use the latter to check that the periods agree with the theoretical result for the detected period:
   T' = (1-v/c) T and T' = (1+v/c) T.
3. Repeat the previous check when the detector moves with a positive (negative) horizontal velocity dx/dt.
4. Repeat the previous checks when the medium moves with a positive (negative) horizontal velocity V_x.
5. (You may also be curious about what happens when dy/dt and/or V_y are non zero.)
6. Use the mouse to put the detector out of the source trajectory, press Initial and then Continue. You should observe that when the wave front reaches the source in a direction perpendicular to the source motion the transverse Doppler effect is nil (but not in special relativity: recall the Ives-Stilwell experiment).
7. Check that in the supersonic case (v ≥ c) a shock wave develops. Press Stop and click the mouse at different points of the shock to check the theoretical angle.