1. Introduction

2.  How does sound move from one place to another?  Is there sound in outer space?  If waves continuously crash on the beach, why doesn’t the ocean pile up on the coast?

3.  Waves we can see (Mechanical Waves) ◦ Waves on water ◦ Waves on a string ◦ Waves in springs ◦ Traffic ◦ Others?  Waves we can’t see (Electromagnetic & other) ◦ Radio waves, microwaves ◦ X-rays ◦ Sound waves ◦ Earthquakes? ◦ Light waves

4.  Energy causes something to vibrate  Vibration is a repeating back and forth or up and down motion ◦ A vibration is a wiggle in time ◦ Think of a bell ringing  A wave is a wiggle that moves in space ◦ A wave moving across the ocean ◦ Sound coming from a bell

5.  Observe the mass bouncing on a spring ◦ Describe as many things as you can about what you see. Click here to see animationhere

6.  Spring with a mass  Pendulum at low swing angles  Bicycle pedal

7.  Mechanical waves require a medium (mass) ◦ Particles are in motion ◦ There is a restoring force ◦ Due to inertia, the mass passes through the resting point to the other side ◦ Can be described with a sine wave

8. Do the wave!

10. http://www.walter-fendt.de/ph14e/stwaverefl.htm

11. TOC Transverse: Wave moves medium moves Longitudinal Wave moves medium moves

12. The wave crests are moving through the water at 1 m/s The wave crests are 1 meter apart The bird sees a wave crest A right now. How long before it sees: Wave crest B? Wave crest C? Wave trough D? ABC D

13. The PERIOD (T) of the wave is the time between two points on the wave that repeat the pattern What is the period of this wave? The FREQUENCY (f) of a wave is how often the wave repeats itself in one second What is the frequency of this wave? Relationship between frequency and period: f = 1/T ABC D

14. The SPEED (v) of a wave is equal to wavelength x frequency v = f

15.  Frequency: f = 1 / T  Period: T = 1 / f )  Velocity: v = f

16. Speedv m/s Wavelength meters PeriodTseconds Frequency fCycles/sec (Hertz)

17.  The spring completes one cycle in 0.5 s. ◦ What is its period, T? ◦ What is its frequency, f? T = 0.5 s f = 1/T = 1/0.5s = 2 Hertz (Hz)

18.  A surfer feels a wave every 10 s. If they are 50 m apart, how fast are the waves moving? v = f, so we need to find f F = 1/T = 1/10s So, v = 50m/10s = 5 m/s

19.  Waves transfer energy without transferring matter  Mechanical waves require a medium  A continuous wave is a regularly repeating sequence of wave pulses