1. Chapter 17

2. A. WHAT ARE MECHANICAL WAVES? 1. What is a Mechanical Wave? It is a disturbance in matter that carries energy from one place to another. 2. What is a medium? It is the material through which a wave travels. Mechanical waves require matter to travel through.

3. 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. B. TYPES OF MECHANICAL WAVES 1. What are the three main types of mechanical waves? Transverse Waves Longitudinal Waves Surface Waves

5. B. TYPES OF MECHANICAL WAVES 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. TRANSVERSE WAVE

6. B. TYPES OF MECHANICAL WAVES 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 TRANSVERSE WAVE

7. B. TYPES OF MECHANICAL WAVES 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. LONGITUDINAL WAVE

8. B. TYPES OF MECHANICAL WAVES 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 LONGITUDINAL WAVE

9. B. TYPES OF MECHANICAL WAVES 6. What is a surface wave? It is a wave that travels along a surface separating two media. An example is an ocean wave. SURFACE WAVES

10. B. TYPES OF MECHANICAL WAVES 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 SURFACE WAVE

11. A. FREQUENCY AND PERIOD 1. 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. 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

15. 3 WAVES QUESTIONS Which wave has the following: Longest wavelength Shortest wavelength Largest amplitude Smallest amplitude Highest frequency Smallest frequency Longest period Shortest period

17. C. WAVE SPEED 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. 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

18. SymbolNameUnitsEquation VVelocityMeters/secondV = λ / T VVelocityMeters/secondV = ν λ λWavelengthMetersλ = V T λWavelengthMetersλ = V / ν TPeriodSecondsT = λ / V νFrequencyHertzν = V / λ

19. 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. A. REFLECTION 1. 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. SIMPLE REFLECTION

21. B. 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. REFRACTION

22. C. 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. DIFFRACTION

23. D. 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 INTERFERENCE

24. D. INTERFERENCE Constructive Interference It occurs when two or more waves combine to produce a wave with a larger displacement. CONSTRUCTIVE INTERFERENCE

25. D. INTERFERENCE Destructive Interference It occurs when two or waves combine to produce a wave with a smaller displacements DESTRUCTIVE INTERFERENCE

26. E. 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. STANDING WAVES

27. E. 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 PARTS OF STANDING WAVES

28. A. PROPERTIES OF SOUND WAVES 1. 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. SOUND WAVES

29. 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. SPEED OF SOUND Medium (at 1 atm)Speed (m/s) Dry air, 0°C331 Dry air, 20°C342 Fresh water, 0°C1401 Fresh water, 30°C1509 Salt water, 0°C1449 Salt water, 30°C1546 Lead, 25°C1210 Cast iron, 25°C4480 Aluminum, 25°C5000 Borosilicate glass, 25°C5170

30. A. PROPERTIES OF SOUND WAVES 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. SOUND INTENSITY DIAGRAM

31. A. PROPERTIES OF SOUND WAVES 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. SOUND INTENSITY LEVEL SoundDecibel Threshold0 Whisper15-20 Normal40-50 Street noise60-70 Inside a bus90-100 Heavy machinery80-120 Rock concert110-120 Pain120 Jet taking off120-160

32. A. PROPERTIES OF SOUND WAVES 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. LOUDNESS

33. A. PROPERTIES OF SOUND WAVES 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. PITCH AND LOUDNESS

34. B. ULTRASOUND & INFRASOUND 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) SOUNDS

35. B. ULTRASOUND & INFRASOUND 10. What is sonar? It is a technique for determining the distance to an object under wave. Sonar stands for sound navigation and ranging. SONAR

36. B. ULTRASOUND & INFRASOUND 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. ULTRASOUND OF HEART

37. D. THE DOPPLER EFFECT 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. 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.

38. 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. E. HEARING AND THE EAR 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. 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.

40. The Anatomy of the ear Figure 19 Page 517

41. 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. 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. G. MUSIC 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. RESONANCE

44. END OF THE CHAPTER Complete the study guide! YOUR TEST IS NEXT!