1. Waves are for SURFING… yeah!
Monterey, CA
Cayucos, CA

2. Get outta there
Ghost tree

3. Q15.1
If you double the wavelength l of a wave on a string, what happens to the wave speed v and the wave frequency f?
A. v is doubled and f is doubled.
B. v is doubled and f is unchanged.
C. v is unchanged and f is halved.
D. v is unchanged and f is doubled.
E. v is halved and f is unchanged.

4. A15.1
If you double the wavelength l of a wave on a string, what happens to the wave speed v and the wave frequency f?
A. v is doubled and f is doubled.
B. v is doubled and f is unchanged.
C. v is unchanged and f is halved.
D. v is unchanged and f is doubled.
E. v is halved and f is unchanged.

5. Representing waves Draw a graph of the wave if:
At t = 0 s the snapshot graph of a wave is…
v = 10 cm/s
Draw a graph of the wave if:
Its amplitude is halved and its wavelength is doubled.
Its speed is doubled and its frequency is quadrupled
Draw a History graph for a “bead” located at x = 0 m.

6. Snapshot and History graphs
Draw the history graph D(x = 0 m, t) at x = 0 m for the wave shown.
Draw the snapshot graph D(x, t = 0) at t = 0 s for the wave shown.

7. Q15.2
Which of the following wave functions describe a wave that moves in the –x-direction?
A. y(x,t) = A sin (–kx – wt)
B. y(x,t) = A sin (kx + wt)
C. y(x,t) = A cos (kx + wt)
D. both B. and C.
E. all of A., B., and C.

8. A15.2
Which of the following wave functions describe a wave that moves in the –x-direction?
A. y(x,t) = A sin (–kx – wt)
B. y(x,t) = A sin (kx + wt)
C. y(x,t) = A cos (kx + wt)
D. both B. and C.
E. all of A., B., and C.

9. A. The velocity is upward. B. The velocity is downward.
Q15.3 y
A wave on a string is moving to the right. This graph of y(x, t) versus coordinate x for a specific time t shows the shape of part of the string at that time.
At this time, what is the velocity of a particle of the string at x = a? x a
A. The velocity is upward.
B. The velocity is downward.
C. The velocity is zero.
D. not enough information given to decide

10. A. The velocity is upward. B. The velocity is downward.
A wave on a string is moving to the right. This graph of y(x, t) versus coordinate x for a specific time t shows the shape of part of the string at that time.
At this time, what is the velocity of a particle of the string at x = a? x a
A. The velocity is upward.
B. The velocity is downward.
C. The velocity is zero.
D. not enough information given to decide

11. A. The acceleration is upward. B. The acceleration is downward.
Q15.4 y
A wave on a string is moving to the right. This graph of y(x, t) versus coordinate x for a specific time t shows the shape of part of the string at that time.
At this time, what is the acceleration of a particle of the string at x = a? x a
A. The acceleration is upward.
B. The acceleration is downward.
C. The acceleration is zero.
D. not enough information given to decide

12. A. The acceleration is upward. B. The acceleration is downward. y
A wave on a string is moving to the right. This graph of y(x, t) versus coordinate x for a specific time t shows the shape of part of the string at that time.
At this time, what is the acceleration of a particle of the string at x = a? x a
A. The acceleration is upward.
B. The acceleration is downward.
C. The acceleration is zero.
D. not enough information given to decide

13. A. The velocity is upward. B. The velocity is downward.
Q15.5 y
A wave on a string is moving to the right. This graph of y(x, t) versus coordinate x for a specific time t shows the shape of part of the string at that time.
At this time, what is the velocity of a particle of the string at x = b? x b
A. The velocity is upward.
B. The velocity is downward.
C. The velocity is zero.
D. not enough information given to decide

14. A. The velocity is upward. B. The velocity is downward.
A wave on a string is moving to the right. This graph of y(x, t) versus coordinate x for a specific time t shows the shape of part of the string at that time.
At this time, what is the velocity of a particle of the string at x = b? x b
A. The velocity is upward.
B. The velocity is downward.
C. The velocity is zero.
D. not enough information given to decide

15. A new swell
A swell arrived last night and the buoys indicated an 18 second period with 3m height. Sweet!! The wave velocity where the buoys are located is 28 m/s and it moves in the positive x direction.
What is the amplitude, angular frequency, wavelength and wave number of the wave?
Write a wave function describing the wave.
A buoy is located at x = 0 m. At time t = 6s the buoy is moving downward with its maximum velocity. Draw a history graph for the buoy. Label x and y axes.
Draw a snapshot graph for the buoy at t = 0s. This graph can be qualitative (no numbers.
Rincon

16. The speed of a transverse wave
Pulse on a string

17. Q15.8
The four strings of a musical instrument are all made of the same material and are under the same tension, but have different thicknesses. Waves travel
A. fastest on the thickest string.
B. fastest on the thinnest string.
C. at the same speed on all strings.
D. not enough information given to decide

18. A15.8
The four strings of a musical instrument are all made of the same material and are under the same tension, but have different thicknesses. Waves travel
A. fastest on the thickest string.
B. fastest on the thinnest string.
C. at the same speed on all strings.
D. not enough information given to decide

19. The speed of a transverse wave II
What happens to wave velocity, frequency and wavelength of waves travelling up the rope?
v , f , l 
v , f =, l 
v , f =, l 
v , f , l =
Not enough information

20. The speed of waves on a string and speed of sound
A note on a bass guitar produces sound waves. The frequency of the string’s oscillations is 20 Hz and the wavelength was 10m. What happens to the velocity, frequency and wavelength of the waves when they leave the guitar and propagate through the air?
v , f , l 
v , f =, l 
v , f =, l 
v , f , l =
Not enough information

21. Q33.1
When light passes from vacuum (index of refraction n = 1) into water (n = 1.333),
A. the wavelength increases and the frequency is unchanged.
B. the wavelength decreases and the frequency is unchanged.
C. the wavelength is unchanged and the frequency increases.
D. the wavelength is unchanged and the frequency decreases.
E. both the wavelength and the frequency change.

22. A33.1
When light passes from vacuum (index of refraction n = 1) into water (n = 1.333),
A. the wavelength increases and the frequency is unchanged.
B. the wavelength decreases and the frequency is unchanged.
C. the wavelength is unchanged and the frequency increases.
D. the wavelength is unchanged and the frequency decreases.
E. both the wavelength and the frequency change.

23. A light wave travels from vacuum, through a transparent material, and back to vacuum. What is the index of refraction of this material? Explain
v = c
v = c

24. Wave intensity
Go beyond the wave on a string and visualize, say … a sound wave spreading from a speaker. That wave has intensity dropping as 1/r2.

25. Thumping bass
You are 3m from your friend’s car, who is pumping obnoxiously loud, bass-heavy music through his subwoofer-equipped car, causing the entire car to rattle. He yells to you that he’s got a 800W subwoofer in his car and its cranked to full volume. Unimpressed, you measure a peak sound intensity of 4.4 W/m2 on your handy Radioshack soundmeter. How many watts is your friend’s subwoofer putting out?
What is the sound intensity for your friend in the car, at 1 m away from the subwoofer?

26. The logarithmic decibel scale of loudness
Our ears can comfortably hear sound over 12 orders of magnitude in intensity!

27. Thumping bass
Your friend has fixed the “problem” with their subwoofer and is now pumping 800W of obnoxiously loud, bass-heavy music through their subwoofer-equipped car, causing the entire car to rattle.
How many dB’s is this at 1 meter away from the speaker?
Why does your friend have an 800W subwoofer instead of an 800W amplifier for all sound frequencies?

28. The Doppler Effect II—moving listener, moving source
As the object making the sound moves or as the listener moves (or as they both move), the velocity of sound is shifted enough to change the pitch perceptively.

29. Q16.8
On a day when there is no wind, you are moving toward a stationary source of sound waves. Compared to what you would hear if you were not moving, the sound that you hear has
A. a higher frequency and a shorter wavelength.
B. the same frequency and a shorter wavelength.
C. a higher frequency and the same wavelength.
D. the same frequency and the same wavelength.

30. A16.8
On a day when there is no wind, you are moving toward a stationary source of sound waves. Compared to what you would hear if you were not moving, the sound that you hear has
A. a higher frequency and a shorter wavelength.
B. the same frequency and a shorter wavelength.
C. a higher frequency and the same wavelength.
D. the same frequency and the same wavelength.

31. Q16.9
On a day when there is no wind, you are at rest and a source of sound waves is moving toward you. Compared to what you would hear if the source were not moving, the sound that you hear has
A. a higher frequency and a shorter wavelength.
B. the same frequency and a shorter wavelength.
C. a higher frequency and the same wavelength.
D. the same frequency and the same wavelength.

32. A16.9
On a day when there is no wind, you are at rest and a source of sound waves is moving toward you. Compared to what you would hear if the source were not moving, the sound that you hear has
A. a higher frequency and a shorter wavelength.
B. the same frequency and a shorter wavelength.
C. a higher frequency and the same wavelength.
D. the same frequency and the same wavelength.

33. Doppler shift from several sources
You are standing at x = 0m, listening to seven identical sound sources. At t = 0, all seven are at x = 343 m and moving shown below. The sound from all seven will reach your ear at t = 1s. 1 2 3 4
50 m/s speeding up
50 m/s, steady speed
50m/s, slowing down
At rest
50 m/s speeding up
50 m/s, steady speed
50m/s, slowing down 5 6 7
Rank in order, from highest to lowest, the seven frequencies f1 to f7 that you hear at t = 1s.

34. A double Doppler shift
What is the frequency of the 300 Hz siren that’s heard by (a) a person in the warehouse and (b) in the police car as it travels towards the warehouse?