1. Waves Objectives: Wave Motion Waves: Frequency, Wavelength, Velocity
Interference of Waves – Standing Waves
Tsunamis

2. Wave Motion Longitudinal Waves Transverse Waves
A vibrating point “drags” its neighbours into motion. As the motion spreads through space – a wave forms
Waves transport ENERGY not MATTER!
The water from the middle of the pond did NOT travel to the edge
Longitudinal
Waves
Transverse
Waves

3. Transverse or Longitudinal?
Doing the “wave” during sports events
[T]
A massive “fender-bender” on the freeway?
[L]
Sound wave
[L]
Sea waves
[T]
You “wiggle” a rope up and down
[T]
Waves along the violin strings
[T]

4. Wave Motion
A vibrating point “drags” its neighbors into motion. As the motion spreads through space – a wave forms
Crest
Frequency
Trough
Wavelength
Wave speed (velocity) : How fast disturbances travel
Wave speed = (frequency) x (wavelength)

5. Wave Motion Wave speed = (frequency) x (wavelength)
A wave with wavelength 10 meters and time between crests of 0.5 second is traveling in water. What is the wave speed?
0.1 m/s
2 m/s
5 m/s
20 m/s

6. Interference of Waves
Two or more waves occur in the same place at the same time
Superposition. The displacement is the sum of the individual displacement to each wave (The effect just “adds up” )
Constructive: Crest on top of Crest (bright)
Destructive: Crest on top of Trough (dark)

7. Standing Wave Patterns
“One Loop”: fundamental frequency fo
“Two Loop”: 2 x fo
“Three Loop”: 3 x fo
Question: You create a 4-loop standing wave pattern with frequency of 100 Hz. With what frequency can you create a 6-loop standing wave pattern?

8. Tsunami Japan 2011 3-D Simulation
3-D Simulation

9. Puzzles
P1. The distance between two crests of a sea wave is 2.0 m. It water moves “up and down” with frequency of 5 Hz, what is the velocity of the wave?
P2. Typical wind waves (sea waves) have adjacent crests separated by about 100 m, frequency of about 0.1 , and reach hight of about 2 m. How fast do they travel?
P3. A 2-loop standing wave pattern is created along a string by sending waves with frequency of 40 Hz. What frequency will create 5-loop patterns?
P4. A tsunami in the deep ocean has a wavelength of up to 200 km even though its height is only 1 m or so. It can travel as fast as 800 km/h. What is its frequency?
P5. If an earthquake happens in the middle of the Pacific, how long before the waters at the California shore will feel the disturbance, if they are about 5,000 km away?