1. Waves http://www.youtube.com/watch?v=OGyRe_SGnck Bill Nye Tsunami

2. What is a wave?
Wave: A repeating disturbance or movement that transfers energy
Examples: ocean waves, sound, light

3. How do waves travel?
Waves travel though matter, this matter is called a medium
Solid: earth
Liquid: water
Gas: air
Light waves do not need a medium to travel through

4. Mechanical Waves Mechanical Waves: can only travel through matter
Transverse waves: the medium moves at a right angles to the direction of the wave
Example: in the ocean
Compressional waves: the medium moves along the same direction of the wave
Example: a coiled spring (slinky), sound waves

5. Waves and Energy
Waves and energy: waves transport energy without transporting matter

6. Sound waves
Sound waves: compressional waves caused by air molecules vibrating
Can travel through solids, liquids and gases

8. Water waves Caused by wind
Anything on the surface of the water absorbs some of the energy of the wave
The size of the waves depends on
Speed of the wind
How long the wind blows
Distance the wind blows over the water

11. Seismic Waves
Seismic waves: waves that travel through the earth’s crust
They transfer some of the energy to the earth and things on the surface of earth (buildings etc.)
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12. Wave properties Crest: the highest point of the wave
Trough: the lowest point of the wave
Wavelength: the distance from trough to trough or crest to crest
Frequency: the number of wavelengths that pass a fixed point in one second (measured in hertz)
1 Hz = 1 wavelength per second
Period: the time it takes for one wavelength to pas a fixed point (measured in seconds)
Amplitude: the height of the wave

13. Sound Waves
Rarefaction: area of the wave that is not as compressed

15. Wave Properties
Amplitude and energy: the higher the amplitude, the more energy the wave is transferring
Frequency and wavelength: the higher the frequency, the shorter the wavelength
Frequency and energy: the higher the frequency the more energy the wave has
Calculating wave speed:
v = ƒλ
λ = v/ƒ
ƒ= v/ λ

16. Learning check What is the material called that waves pass through?
What type of wave is above?
What causes waves in the ocean?
Which part is the trough?
Crest?
Amplitude?
Wavelength? c d

17. Learning Check
8. Frequency is measured in _____________. 9. What is the equation to find out the speed of a wave? 10. Which wave has the longest wavelength? 11. Which wave has the highest frequency? 12. Which wave has the most energy?

18. Behavior of waves
Reflection: when a wave strikes an object and bounces off of it
Light: reflection in a mirror
Sound: echoes in a canyon

19. The Law of Reflection
The Law of Reflection: the angle of incidence is equal to the angle of reflection

20. Refraction
Refraction: the bending of a wave caused by a change in its speed as it moves from one medium to another
The wave bends more when there is a greater change in speed between the 2 substances

22. Diffraction
Diffraction: when an object causes a wave to change direction and bend around it

23. Diffraction of sound
Sound waves diffract around openings in solid surfaces easily

24. Diffraction and light
Light waves are tiny so diffraction doesn’t affect them very much

26. Diffraction Light bending to create invisibility

27. Radiowaves
AM frequency waves have longer wavelengths than FM radiowaves
AM radiowaves can diffract around buildings and mountains much easier so the reception is clearer
FM radiowaves sound much clearer but have a shorter range

28. Interference Interference: when 2 waves combine to make a new wave

29. Interference
Constructive interference: two waves over lap and their amplitudes are added together
Crest lines up with crest
Said to be “in phase”

30. If this was a sound wave, what would happen to the sound?
If this was a water wave, what would happen to the water?
If this was a light wave, what would happen to the light?

31. Interference
Destructive interference: two waves overlap and their amplitudes are subtracted
Crest of 1st wave meets trough of the 2nd wave
Said to be “out of phase”

32. If this was a sound wave, what would happen to the sound?
If this was a water wave, what would happen to the water?
If this was a light wave, what would happen to the light?

33. Standing Waves http://www.youtue.com/watch?v=NpEevfOU4Z8
Standing wave: when waves that have the same wavelength and amplitude traveling in opposite directions interfere with each other
Nodes: places where 2 standing waveswaves cancel each other
Antinodes: where vibrating occurs between nodes

34. Standing waves in music
Violin or guitar string: vibrates creating a standing wave
Flute: vibrates a column of air creating a standing wave
Drums: vibrates a tightly stretched material creating a standing wave
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35. Resonance http://www. youtube. com/watch. v=1yaqUI4b974 http://www
Resonance: an object vibrates by absorbing energy at its natural frequencies
If enough energy is put in, the object could break apart
Bridge affected by constructive interference of its natural resonance frequency
Resonance and tuning forks

36. Learning Check
What is it called when waves overlap and either increases or decrease their effect?
What is it called when a wave bounces off an object and returns?
What is it called when a wave bends when it travels around an object?
What is it called when light bends when it enters a different medium?
All objects vibrate at a natural frequency called ________________.

37. Learning Check
6. Which type of radiowave will give you better reception if you are traveling through the mountains? 7. If 2 waves combine to make a bigger wave it is called ______________________. 8. If 2 waves combine to make a smaller wave, it is called _____________________.