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Mechanical Waves and Sound

Chapter 17. Mechanical Waves and Sound. Chapter 17.1 Mechanical Waves. A. What are Mechanical Waves?. 2. What is a medium? It is the material through which a wave travels. Mechanical waves require matter to travel through. What is a Mechanical Wave?

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Mechanical Waves and Sound

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  1. Chapter 17 Mechanical Waves and Sound

  2. Chapter 17.1Mechanical Waves A. What are Mechanical Waves? 2. What is a medium? It is the material through which a wave travels. Mechanical waves require matter to travel through. • What is a Mechanical Wave? It is a disturbance in matter that carries energy from one place to another.

  3. Chapter 17.1Mechanical Waves A. What are Mechanical Waves? 3. How are mechanical waves created? They are created when a source of energy causes a vibration to travel through a medium. (Vibration is a repeating back-and-forth motion.)

  4. Chapter 17.1Mechanical Waves B. Types of Mechanical Waves • What are the three main types of mechanical waves? Transverse Waves Longitudinal Waves Surface Waves

  5. Chapter 17Mechanical Waves B. Types of Mechanical Waves Transverse Wave 2. What is a transverse wave? It is a wave that causes the medium to vibrate at right angles to the direction in which the wave travels. An example is shaking crumbs off a picnic blanket.

  6. Chapter 17Mechanical Waves B. Types of Mechanical Waves Transverse Wave 3. Simple diagram of a transverse wave Crest  the highest point of the wave above the rest position Trough  the lowest point of the wave below the rest position

  7. Chapter 17.1Mechanical Waves B. Types of Mechanical Waves Longitudinal Wave 4. What is a longitudinal Wave? It is a wave in which the vibration of the medium is parallel to the direction the wave travels. An example is a slinky.

  8. Chapter 17.1Mechanical Waves B. Types of Mechanical Waves Longitudinal wave 5. Simple diagram of a longitudinal wave Compression  an area where the particles in a medium are spaced close together Rarefaction  an area where the particles in a medium are spread out

  9. Chapter 17.1Mechanical Waves B. Types of Mechanical Waves Surface waves • What is a surface wave? It is a wave that travels along a surface separating two media. An example is an ocean wave.

  10. Chapter 17.1Mechanical Waves B. Types of Mechanical Waves Surface wave 7. Simple diagram of a surface wave. Crest  the highest point of the wave above the rest position Trough  the lowest point below the rest position

  11. Chapter 17.2Properties of Mechanical Waves Frequency and Period B. Wavelength and Amplitude 3. What is wavelength? It is the distance between a point on one wave and the same point on the next cycle of the wave 4. What is amplitude? It is the maximum displacement of the medium from its rest position • What is periodic motion? Any motion that repeats at regular time intervals. 2. What is a period? The time required for one cycle, a complete motion that returns to its starting point.

  12. Chapter 17.2Properties of Mechanical Waves

  13. Chapter 17.2Properties of Mechanical Waves

  14. Chapter 17.2Properties of Mechanical Waves

  15. Chapter 17.2Properties of Mechanical Waves 3 Waves Questions Which wave has the following: Longest wavelength Shortest wavelength Largest amplitude Smallest amplitude Highest frequency Smallest frequency Longest period Shortest period

  16. Chapter 17.2Properties of Mechanical WavesDiagram of three waves

  17. Chapter 17.2Properties of Mechanical Waves C. Wave Speed 7. How do you calculate wave speed? Speed of wave = wavelength divided by period V = λ ÷ T Speed of wave = wavelength times frequency V = λ•ν 5. What is wave speed? It is how fast the wave is traveling. 6. Statement: If you assume that waves are traveling at a constant speed, then wavelength is inversely proportional to frequency.

  18. Chapter 17.2Properties of Mechanical Waves

  19. Chapter 17.2 Properties of Mechanical Waves 8. Math Skills on page 506 List, formula, substitution, work, answer 9. Math Practice on page 506 4.0 m/s 0.4 m/s 50 cm/s .5 Km 10. Math Practice on page 507 4.0 m/s .5 s

  20. Chapter 17.3Behavior of Waves A. Reflection Simple Reflection • What is reflection? It occurs when a wave bounces off a surface that it cannot past through. Reflection does not change the speed or frequency of a wave, but the wave can be flipped upside down.

  21. Chapter 17.3Behavior of Waves B. Refraction Refraction 2. What is refraction? It is the bending of a wave as it enters a new medium at an angle. When a wave enters a medium at an angle, refraction occurs because one side of the wave moves slowly than the other side.

  22. Chapter 17.3Behavior of Waves C. Diffraction Diffraction 3. What is diffraction? It is the bending of a wave as it moves around an obstacle or passes through a narrow opening. A wave diffracts more if its wavelength is large compared to the size of an opening or obstacle.

  23. Chapter 17.3Behavior of Waves D. Interference Interference 4. What is interference? It occurs when two or more waves overlap and combine together. 5. What are the two types of interferences? Constructive Interference Destructive Interference

  24. Chapter 17.3Behavior of Waves D. Interference Constructive Interference Constructive Interference It occurs when two or more waves combine to produce a wave with a larger displacement.

  25. Chapter 17.3Behavior of Waves D. interference Destructive interference Destructive Interference It occurs when two or waves combine to produce a wave with a smaller displacements

  26. Chapter 17.3Behavior of Waves e. Standing waves Standing waves 6. What are standing waves? It is a wave that appears to stay in one place—it does not seem to move through the medium A standing wave forms only if half a wavelength or a multiple of half a wavelength fits exactly into the length of a vibrating cord.

  27. Chapter 17.3Behavior of Waves e. Standing waves Parts of standing waves 7. What are the parts of a standing wave? Node  a point on a standing wave that has no displacement from the rest position Antinode  a point where a crest or trough occurs midway between two nodes

  28. Chapter 17.4Sound and Hearing Properties of Sound waves Sound waves • Statement: Sound waves are longitudinal waves—compressions and rarefactions that travel through a medium. 2. Many behaviors of sound can be explained using a few properties--speed, intensity and loudness, and frequency and pitch.

  29. Chapter 17.4Sound and Hearing Speed of sound Speed of sound 3. How does temperature affect the speed of sound? Higher the temperature, greater the speed of sound. 4. How does the type of material affect the speed of sound? Sound travels faster in solids than liquids than gases.

  30. Chapter 17.4Sound and Hearing Properties of Sound Waves Sound intensity diagram 5. What is Intensity? It is the rate at which a wave’s energy flows through a given area. Sound intensity depends on both the wave’s amplitude and the distance from the sound source.

  31. Chapter 17.4Sound and Hearing Properties of Sound waves Sound intensity level 6. What is the unit for sound intensity levels? The decibel (dB) is a unit that compares the intensity of different sounds. The decibel scale is based on powers of ten. For every 10-decibel increase, the sound intensity increases tenfold.

  32. Chapter 17.4Sound and Hearing Properties of Sound waves loudness 7. What is loudness? It is a physical response to the intensity of sound, modified by physical. It is subject to a person’s interpretation. It depends on factors such as the health of your ears and how your brain interprets the information in sound waves.

  33. Chapter 17.4Sound and Hearing Properties of Sound Waves Pitch and loudness 8. What is the relationship between frequency and pitch? Pitch is the frequency of a sound as you perceive it. The frequency of a sound wave depends on how fast the source of the sound is vibrating. Pitch also depends on other factors such as your age and the health of your ears.

  34. Chapter 17.4Sound and Hearing B. Ultrasound & Infrasound Sounds 9. What is the difference between infrasound and ultrasound? Infrasound is sound at frequencies lower than most people can hear (20 Hz). Ultrasound is sound at frequencies higher than most people can hear (20,000 Hz)

  35. Chapter 17.4Sound and Hearing B. Ultrasound & Infrasound Sonar 10. What is sonar? It is a technique for determining the distance to an object under wave. Sonar stands for sound navigation and ranging.

  36. Chapter 17.4Sound and Hearing B. Ultrasound & Infrasound Ultrasound of heart 11. What is ultrasound imaging? It is an important medical technique. A pulse is sent into a patient. Each pulse is short—about 1/8000 of a second—so that it doesn’t interfere with the reflected pulse.

  37. Chapter 17.4Sound and Hearing D. The Doppler Effect 13. What is the relationship between frequency and movement? As a source of sound approaches, an observer hears a higher frequency. When the sound source moves away, the observer hears a lower frequency. 12. What is the Doppler effect? It is the change in sound frequency caused by motion of the sound source, motion of the listener, or both. It was discovered by the Austrian scientist Christian Doppler.

  38. Chapter 17.4Sound and Hearing Diagram of Doppler Effect 14. What is happening to the frequency and wavelength when the ambulance is approaching? 15. What is happening to the frequency and wavelength when the ambulance is receding?

  39. Chapter 17.4Sound and Hearing E. Hearing and the Ear 17. The outer ear gathers and focuses sound into the middle ear, which receives and amplifies the vibrations. The inner ear uses nerve endings to senses vibrations and send signals to the brain. 16. Statement! The ear is a complex system that consists of three main regions—the outer ear, the middle ear, and the inner ear—as shown on the next page.

  40. Chapter 17.4Sound and Hearing The Anatomy of the ear Figure 19 Page 517

  41. Chapter 17.4Sound and Hearing f. How sound is Reproduced 18. How is sound recorded and reproduced? Sound is recorded by converting sound waves into electronic signals that can be processed and stored. Sound is reproduced by converting electronic signals back into sound waves.

  42. Chapter 17.4Sound and Hearing G. Music 19. Statements! Musical instruments can produce a wide variety of sounds. This is possible because most musical instruments vary pitch by changing the frequency of standing waves.

  43. Chapter 17.4Sound and Hearing G. Music Resonance 20. What is resonance? It is the response of a standing wave to another wave of the same frequency. It can produce a dramatic increase in amplitude.

  44. Chapter 17Mechanical Waves and Sound End of the chapter Your test is next! Complete the study guide!

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