1. Waves

2. Section 1 & 2 Objectives Explain how forces cause waves Explain how waves transfer energy Classify wave types Calculate a wave’s speed Identify properties of waves

3. The Basics Waves transfer ENERGY and are caused by FORCES.

4. PARTS OF A WAVE A.AMPLITUDE measures the height of each wave crest B. WAVE LENGTH is the distance between 2 crests of a wave, or between 2 troughs C. FREQUENCY is the number of waves that hit an object in a given period of time D. As frequency increases, WAVE LENGTH decreases E. CREST is tallest point F. TROUGH is the lowest point G. Increase the speed of disturbance, you increase the FREQUENCY.

5. THE WAVE http://www.youtube.com/watch?v=- 5zmRt4bL8A&safety_mode=true&persist_safety_mod e=1&safe=active http://www.youtube.com/watch?v=- 5zmRt4bL8A&safety_mode=true&persist_safety_mod e=1&safe=active

6. GRAPHING A WAVE PAGE 499

7. CALCULATIONS To find speed of the wave you use the formula SPEED=FREQUENCY X WAVE LENGTH To find the frequency of waves you DIVIDE NUMBER OF WAVES BY THE TIME IT TOOK TO GET TO A CERTAIN POINT If the crest of two waves join up exactly, their amplitudes are ADDED

8. TYPES OF WAVES MECHANICAL WAVES are caused by forces creating a disturbance in a medium. EX)SOUND, WATER, WAVES MADE BY A ROPE LONGITUDINAL WAVES Occur when energy travels in the same direction as the disturbance EX) SOUND TRANSVERSE WAVES Transfers energy at right angles to the disturbance Ex)WATER WAVES

9. Types of Waves ELECTROMAGNETIC WAVES Are caused by a disturbance that transfers energy through a field EX) LIGHT WAVES, MICROWAVES, RADIO WAVES

10. Section 3 Objectives Describe how waves change as they encounter a barrier Explain what happens when waves enter a new medium Identify ways in which waves interact with one another

11. Reflection 1. REFLECTION is the reaction when a waves hits a barrier and cannot pass through it EX) ECHO IN A CANYON EX) IF YOU PUT A SOLID WOOD BARRIER COMPLETELY ACROSS A TANK FULL OF WATER, WAVES IN THE TANK WILL BE REFLECTED BY THE WOOD

12. REFRACTION 2. REFRACTION occurs because waves move through different mediums at different speeds EX)WHEN YOU PUT A STICK INTO A POND AND THE STICK APPEARS TO BE “BROKEN”

13. DIFFRACTION DIFFRACTION is the spreading out of waves through an opening or around the edge of an obstacle. EX)WATER BENDING AROUND A ROCK IN THE RIVER, POND SPREADS OUT PAST A ROCK IN A POND, SHADOW ON THE GROUND

14. Interference Waves interact with one another They can add energy to another wave They can take energy away from another wave There are two types of interference: constructive & destructive

15. Interference Destructive interference can cancel another wave out EX) A quiet spot in the classroom during a movie is cause by destructive interference Constructive interference occurs when the crests & troughs of tow waves align exactly EX) When a wave moves across a pond, it transfers water molecules up and down and energy across the pond EX) When a wave passes through the ocean, energy is transferred across great distances while individual areas move up and down

16. Forces & Wave Forces cause waves by creating DISTURBANCES EARTHQUAKES Are caused when forces inside earth cause rocks to move. Earthquake waves are produced and carry kinetic energy through the ground. Roads bent of broken far from the earthquake’s center shows that waves TRANSFER ENERGY OVER DISTANCE A moving object has KINETIC ENERGY. It has the most when it is moving the fastest.

17. Section 1 Objectives Explain how sound waves are produced & detected Explain how sound waves transfer energy Describe what effects the speed of sound waves

18. Sound Waves SOUND WAVES Are caused by vibrations. Sound waves transfer energy by PUSHING AIR PARTICLES The sound of your voice is created by FORCING AIR THROUGH YOUR VOCAL CHORDS MAKING THEM VIBRATE

19. PAGE 518 & 519 IN BOOK

20. Section 3 Objectives o Explain how the intensity of a wave affects its loudness o Describe how sound intensity can be controlled o Explain how loudness can affect hearing

21. Intensity of Sound (Decibels) The intensity of sound is determined by its amplitude, or the amount of energy carried by a wave.

22. Intensity of Sound

23. Sound becomes SOFTER at a distance because the energy of a sound wave is SPREAD OUT OVER A GREATER AREA A CAR MUFFLER & ACCOUSTIC TILES makes sound softer by absorbing energy from sound waves.

24. Amplification Increasing strength of an electrical signal Increases the intensity of a sound wave Sound is converted into vibrations in a coil which is attached to a cone to magnify the sound

25. Acoustics Scientific study of sound How it is produced and how it is received by humans & animals The way waves behave inside a space Reduce unwanted echoes

26. SOUND IN A VACUUM ROBERT BOYLE PLACE A TICKING CLOCK IN A SEALED JAR AND REMOVED AIR PARTICLES HE HEARD NO TICKING ONCE ALL AIR WAS REMOVED HE PROVED THAT SOUND DOES NOT TRAVEL THROUGH A VACCUM

27. Speed of Sound Depends on medium Faster through liquid than gases Also can travel through solid elastic mediums (steel) Sound travels faster through a medium at a higher temperature than a lower one Sound travels slower than light

28. Section 2 Objectives Describe how the frequency of a wave affects the way it sounds Describe how sound quality differs from pitch Learn about the Doppler Effect

29. PITCH Pitch: HIGHNESS & LOWNESS of a sound To raise the pitch of a sound, you can INCREASE THE FREQUENCY of the wave. To lower the pitch, you can DECREASE THE FREQUENCY of the wave.

30. PITCH As sound passes by, PITCH WILL INCREASE A motorcycle’s sound is at A HIGHER PITCH when it is coming toward you than going away from you. If you play the same pitch on two different instruments, the notes may sound different because of OVERTONES

31. Natural Frequency Every object has a frequency at which it vibrates EX) piano tuner Strengthening the sound wave is called resonance

32. Sound Quality “Timbre” Most sounds are not single waves, but are a combination of waves This is why two singers can sing the exact same note, but sound different

33. Doppler Effect Change in perceived pitch that occurs when the source or the receiver of sound is moving http://www.youtube.com/watch?v=Gpe6zIKmoWA&s afety_mode=true&persist_safety_mode=1&safe=active http://www.youtube.com/watch?v=Gpe6zIKmoWA&s afety_mode=true&persist_safety_mode=1&safe=active

34. ULTRASOUND Ultrasounds waves are a type of SOUND wave that can be used by bats for locating & avoiding objects, Doctors can use ultrasounds waves to LOCATE AND EXAMINE INTERNAL ORGANS

35. Sonar

36. SOUND WAVES CAN DAMAGE HEARING (Page 536) You can damage you hearing by listening to HIGH-INTENSITY SOUNDS You actually damage the HAIR CELLS of the cochlea.

37. How musical instruments work Page 541

38. Telephone Sound waves travel through wires in a telephone Sound waves travel though microwaves in a cell phone Vibrations turn into electrical signals The receiver has a diaphragm that helps produce the sound waves

39. Recorded Sound Edison’s phonograph (Page 543) A CD is hard plastic that has millions of microscopic pits arranged in a spiral. The pits contain info that CD players can turn into electrical signals which are then turned into sound waves.