1. Physics 7C SS1 Lecture 2: Waves
Total Phase…
and Implications for Interference

2. Agenda Get clickers working Review Simple Harmonic Wave model
Introduce total phase
Phase chart representation
Graphing practice (briefly)
Introduce interference (briefly)
A common wave: sound
Wavefront representation

3. Longitudinal vs. Transverse Wave Polarization`
Longitudinal Wave
Transverse Wave

4. Clicker Setup: Joining Class
Turn on your clicker; It scans for Classes
If it doesn’t scan automatically, hit enter (green button)
Find SS1PHY7C; hit enter
Display reads “ANS: SS1PHY7C;” hit enter
When you’ve successfully joined, display reads “ANS: wait for Q”

5. PRS Clicker Setup: Student ID
Turn on your clicker
Press * to access Setup Menu
Scroll to find “ID;” hit Enter (green button)
Enter your Student ID so I can give you credit; hit enter

6. Check Clicker Setup In DL on Tuesday and Wednesday we talked about…
A) Three-phase diagrams and the heat pack
B) Connections between angular and linear variables, such as torque and force
C) Waves and Oscillators
D) Steady-state fluid flow
E) Slow down--I didn’t get my ID entered yet!

7. Source vs. Medium Frequency depends on… A) Source B) Medium C) Neither
D) Both

8. Source vs. Medium Wave Speed depends on… A) Source B) Medium
C) Neither
D) Both

9. Source vs. Medium Period depends on… A) Source B) Medium C) Neither
D) Both

10. Source vs. Medium Wavelength depends on… A) Source B) Medium
C) Neither
D) Both

11. Applying the concepts: Transmission to 2nd Machine
When the wave travels from one machine to the next, which parameters change?
A) Frequency, period, wavelength, and wave speed all change
B) Frequency, period and wavelength
C) Frequency and wavelength
D) Wavelength and wave speed
E) Only wave speed

12. Applying the concepts: Transmission to 2nd Machine
When the wave travels from one machine to the next, which parameters change?
A) Frequency, period, wavelength, and wave speed all change
B) Frequency, period and wavelength
C) Frequency and wavelength
D) Wavelength and wave speed
E) Only wave speed

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

14. 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

15. 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

16. Fixed Phase Constant
Which of the following lists only points with a fixed phase constant of exactly to /2?
A) All
B) ABC
C) ADG
D) AEH
E) ACF

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

18. 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

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

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

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

22. 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 =  f (note meters per second)

23. Wavefront Representation

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