CH 15 & 16

1. CH 15 & 16 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 E. CRESTis tallest point • 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 • AMPLITUDEmeasures the height of each wave crest • D. As frequency increases, WAVE LENGTHdecreases G. Increase the speed of disturbance, you increase the FREQUENCY. F. TROUGHis the lowest point

5. THE WAVE • http://www.youtube.com/watch?v=-5zmRt4bL8A&safety_mode=true&persist_safety_mode=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 areADDED

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 WAVESAre 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 • Explain how the intensity of a wave affects its loudness • Describe how sound intensity can be controlled • 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 • A CD player produces ELECTRICAL SIGNALS which can be used to make SOUND WAVES • When you turn up the CD player, you change the sound’s INTENSITY • A sound wave has a frequency of 300 hertz. How many complete wavelengths pass a given point? = 300 WAVELENGTHS 1 HERTZ= 1 WAVE/SECOND

23. Intensity of Sound • 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&safety_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 echolocation

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.