1. Waves

2. What is a wave?
 - a repeating disturbance or movement that transfers energy through matter or space
Examples:
ocean waves
light
sound

3. Waves 1. Mechanical waves- require a medium to travel through
2. Electromagnetic waves- can move through a vacuum

4. Waves travel through matter - this is called the MEDIUM
Mediums can be - solid  (earth)
- liquid (water)
- gas  (air)
Light and radio waves travel through space and do not need a medium.

5. Transverse Waves - medium moves at a right angle to the direction of the wave (like in the ocean)
Compression waves - medium moves along the same direction as the wave, visualize a coiled spring.

6. Sound waves are compressional waves caused by air molecules vibrating, like when a door slams Sound waves can also travel through other mediums, like earth and water         Wave Animations

7. RAREFACTION = area of wave where it is less compressed
You can use a Slinky to get a good idea of how compressional waves, such as sound, move. Stretch a Slinky out and then give one end a good strong knock or jiggle. This will push the coils near your hand into the ones next to them, which will be pushed into the next and the next and so on, all the way to the other end. At the other end, the compression will rebound and move back in the other direction. Thus a "compression" moves back and forth.
RAREFACTION = area of wave where it is less compressed

8. The Parts of a Transverse Wave
The high part of the wave is the CREST
The low part of the wave is the TROUGH
Amplitude- distance from midpoint to crest or trough

9. The Parts of a Transverse Wave
Wavelength = the distance from one point of the wave to the next point (from crest to crest, or from trough to trough)

10. The Parts of a Transverse Wave
FREQUENCY =  number of waves that pass a point in a second
Frequency is measured in hertz (Hz)
Each wave has a PERIOD, which is the amount of time it takes for one wavelength to pass a point

11. If you make transverse waves by moving a rope up and down, you can increase the frequency by moving the rope faster. This makes the wavelength SHORTER high frequency = short wavelength low frequency = long wavelength

12. Wave Speed - how fast a wave travels    Speed (m/s) =  frequency (Hz)  x wavelength (m)
Greek letter lambda is used to represent wavelength

13. Wave Amplitude
Amplitude is related to the amount of energy a wave carries.
Tighter packed coils of the slinky will cause greater energy.
In the rope, raising the hand higher and causing "bigger" waves increases the amplitude
Amplitude = height of wave

14. Problems
If a water wave vibrates up and down three times each second between wave crests is 2m, what is the wave’s frequency? It’s wavelength? It’s wave speed?

15. If water waves vibrate up and down two times each second and the distance between wave crest is 1.5m, what is the frequency of the wave? Wavelength? Speed?
Frequency- 2 waves/s= 2 Hz
λ= 1.5 m
V= f λ

16. What is the wavelength of a 340 Hz sound wave when the speed of sound in air is 340m/s?

17.  The material a wave passes through (such as water or air) is called the _________________.
Waves that need mediums:___________
Waves that don’t need mediums: ______________
4.  What type of wave is this?
          ________________
Label the parts of the wave.
5.  Wavelength ____
6.  Crest ____ 7.  Amplitude ____ 8.  Trough ____

18. 9.  Which of these waves has a higher frequency?
10.  Define Frequency. Frequency is measured with what unit? How is that unit defined?
11.  What is the equation used to calculate wave speed? B A

19. Wave Interactions 1. Reflection 2. Refraction 3. Diffraction
4. Interference
5. Resonance

20. 1. Wave Reflection  Waves bounce off objects and reflect back the direction they came. With sound waves, this creates an echo. Light and sound both travel in waves. Both can be reflected!

21. The Law of Reflection uses math to determine the angle a wave (light or sound) will reflect.   
You can witness this law in action using a laser pointer and a mirror

22. 2. What is REFRACTION
Why does this straw appear broken at the point it enters the water?
Refraction is the bending of a wave caused by a change in speed as it moves from one medium to another.

23. Light refraction can make it very difficult to catch fish in water, they are not actually where they appear to you...

24. Light passes through a prism
What causes a rainbow?
Light passes through a prism
Visible light is separated into its different wavelengths (7)
R.O.Y.G.B.I.V
This effect can be caused by water droplets

25. 3. What is diffraction? When waves bend around objects
Light waves don't bend around a barrier, but sound waves do. 
Wave Applet

26. AM vs FM radios FM radios have a short wavelength
AM radios have a long wavelength
AM radio waves can diffract around large building and mountains, reception is often better with AM.
FM has superior sound quality but a shorter range.

27. 4.Interference -waves overlap,forming a new wave
Constructive = waves add together, if these are sound waves, the sound becomes louder
Destructive = one wave counters the other, decreasing loudness
*these waves are said to be OUT OF PHASE
Watch what happens when a bridge is subject to constructive interference from wind: Tacoma Narrows  

28. Standing Waves - waves are traveling in opposite directions with the same  wavelength and amplitude
This is difficult to visualize, so lets watch the video of a standing wave being formed in a tank.
How would you describe this wave?
Many instruments rely on standing waves for sound
Ex.  Violin, Drum, Flutes (using air waves)

29. Standing Waves - waves are traveling in opposite directions with the same  wavelength and amplitude
How would you describe this wave?
Produced when two sets of waves of equal amplitude and wavelength pass through each other in opposite directions
Nodes –destructive interference
Antinodes- constructive interference
Many instruments rely on standing waves for sound
Ex.  Violin, Drum, Flutes (using air waves)

30. 5. RESONANCE  All objects have their own natural frequencies of vibration, which depend on size, materials and shapes.  Every bell sounds different Resonance refers to the vibration of an object as it absorbs energy at its natural frequency Check out how tuning forks have their own frequencies.
Bridge Resonance

31. QUIZ  TIME
(only covers last half of notes)

32. Match the term to its description.
1.  When waves overlap and either increase or decrease the effect.
2.  When a wave bounces off an object and returns
3. When a wave bends as it travels around an object
4.  Objects have their own natural frequencies
5.  Created when two waves travel in opposite directions
6.  When light bends as it changes medium (like going from air to water)
A.  resonance
B.  diffraction
C.  refraction
D.  standing waves
E.  interference
F.  reflection