1. Physics 11
Mr. Jean
January 5th, 2012

2. The plan: Dates for Test Standing Waves (reviewed) Visible spectrum
Doppler Effect
Shock Waves
Pendulum Lab tomorrow

3. Possible Test Dates:

4. Interference is a characteristic of all waves.

5. Standing Waves
When two sets of waves of equal amplitude and wavelength pass through each other in opposite directions, it is possible to create an interference pattern that looks like a wave that is “standing still.” It is a changing interference pattern.
Demo - Rope and strobe
Demo - Mechanical overhead model

6. Visible Spectrum:

7. DOPPLER EFFECT
Refers to the change in frequency when there is relative motion between an observer of waves and the source of the waves
Doppler Movie - URL

8. When a source of waves and an observer of waves are getting closer together, the observer of the waves “sees” a frequency for the waves that is higher than the emitted frequency.
When a source of waves and an observer of waves are getting farther apart, the observer of the waves “sees” a frequency for the waves that is lower than the emitted frequency.

9. All waves exhibit the Doppler effect.
A particularly interesting example is used by astronomers to determine if light emitting objects (such as stars) are getting closer to us or farther away.
On average most stars are moving farther away, and their light spectra are “red shifted.”

11. Red Shift: Moving Away from source
Actual Visual Spectrum
Observed Visual Spectrum

12. Blue Shift: Moving towards source
Actual Visual Spectrum
Observed Visual Spectrum

14. Radar bounced off a spinning planet can exhibit a Doppler effect and lead to a determination of the spin rate of the planet.
This was used to discover that Venus has a retrograde spin.
Of course police use the Doppler effect to catch speeding motorists.

17. BOW WAVES Waves in front of moving object pile up.
The familiar bow wave generated by a speedboat knifing through the water is a non-periodic wave produced by the overlapping of many periodic circular waves. It has a constant shape.

20. Video Demonstration:
Demo 2.1 – Waves & Wake from Phys123

21. SHOCK WAVES
Just as circular waves move out from a swimming bug, spherical waves move out from a flying object. If the object flies faster than the waves, the result is a cone-shaped shock wave.
There are two booms, one from the front of the flying object and one from the back.

22. Video Demonstrations:

23. Subsonic
- slower than the speed of sound
Supersonic
- faster than the speed of sound
speed of object
Mach Number =
speed of sound

24. Pendulum Mini-Lab tomorrow