1. Quiz 1

2. Physics 7C SS1 Lecture 2: Wave Model
Total Phase…
and Implications for Interference

3. Agenda Review Simple Harmonic Wave model Introduce total phase
Graphing practice (briefly)
Introduce total phase
Phase chart representation
Introduce interference
Causes of interference types
Lots of waves: good thing is once we know the wave model, we can apply it to any situation with a wave.

4.   The Total Phase Making sense of the wave equation:
Using Total Phase Charts: 2π
 2π  
Unit circle
Wave 1

5. Total Phase
Which of the following includes only points with a total phase of exactly /2?
A) All
B) ABC
C) ADG
D) AEH
E) ACF

6. Total Phase
Which of the following includes only points with a total phase equivalent to /2?
A) All
B) ABC
C) ADG
D) AEH
E) ACF

7. Fixed Phase Constant
Which of the following lists only points with a fixed phase constant of exactly to /2?
A) All (The wave paramaters apply at all peaks. They share the same amplitude, equilibrium, wavelength, period, and fixed phase constant)
B) ABC (These were all at t=0 s for different positions)
C) ADG (These were all at x=0 m for different times)
D) AEH (These were all at peaks--quite likely the same peak that had traveled, and thus =/2)
E) ACF (These were all at peaks, though at least A and C were different peaks.  at each is equivalent to /2)

8.   The Total Phase Making sense of the wave equation:
Using Total Phase Charts: 2π
 2π  
Unit circle
Wave 1

9. Interference: When Waves Meet
Phenomena:
Interfering pulses on the wave machine
Interfering block-wave
Using Total Phase
Equivalent total phase: Constructive
Total phase separated by half-cycle: Destructive

10. A vibrating object acts as the source of the wave
A vibrating object acts as the source of the wave. As a speaker moves through a cycle, it fixes the period and frequency.
A = Amplitude, controlled by what starts the wave
T = Period, how long to get back to where it started
 = Wavelength, repeat distance in space
T = where f is the frequency
Velocity v = 

11. Interfering Sound Waves
What type of interference would result?
Constructive
Destructive
Partial
No interference

12. Interfering Sound Waves+
Greater pressure fluctuations
More & less intense means louder and softer
Greater amplitude

13. Interfering Sound Waves+
Greater pressure fluctuations
More & less intense means louder and softer
Amplitude is zero

14. Phase Chart for Interfering Waves
Same rough format, but add difference (most important part!) 2π
 2π  
Unit circle
Wave 1
Wave 2
Difference

15. What factors might influence type of interference?2π
 2π  
Unit circle
Wave 1
Wave 2
Difference
Anything that helps determine total phase!!!

16. What is responsible for the destructive interference in this case?
x=0
x=/2
x

None of the above

17. What is responsible for the destructive interference in this case?
x=0
x=/2
x

None of the above
(and other terms like =0)

18. Interference for differing frequencies: Beats.1 2 3 4 5
What type of interference occurs at each point?

19. Wavefront Representation

20. Wavefront Representation
How long is the marked distance?
/2 
T/2 T