mechanical waves and sound
DESCRIPTION
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? - PowerPoint PPT PresentationTRANSCRIPT
Mechanical Waves and Sound
Chapter 17
Chapter 17.1Mechanical WavesA. 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.
Chapter 17.1Mechanical WavesA. 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.)
Chapter 17.1Mechanical WavesB. TYPES OF MECHANICAL WAVES
1. What are the three main types of mechanical waves?
Transverse Waves
Longitudinal Waves
Surface Waves
Chapter 17Mechanical WavesB. 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
Chapter 17Mechanical WavesB. TYPES OFMECHANICAL 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
Chapter 17.1Mechanical WavesB. 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
Chapter 17.1Mechanical WavesB. 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
Chapter 17.1Mechanical WavesB. TYPES OFMECHANICAL 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
Chapter 17.1Mechanical WavesB. 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
Chapter 17.2Properties of Mechanical WavesA. 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
Chapter 17.2Properties of Mechanical Waves
Chapter 17.2Properties of Mechanical Waves
Chapter 17.2Properties of Mechanical Waves
Chapter 17.2Properties of Mechanical Waves
3 WAVES QUESTIONS
Which wave has the following:
Longest wavelengthShortest wavelengthLargest amplitudeSmallest amplitudeHighest frequencySmallest frequencyLongest periodShortest period
Chapter 17.2Properties of Mechanical WavesDiagram of three waves
Chapter 17.2Properties of Mechanical Waves
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 ÷ TSpeed of wave =
wavelength times frequency
V = λ • ν
Chapter 17.2Properties of Mechanical WavesSymbol Name Units EquationV Velocity Meters/second V = λ / TV Velocity Meters/second V = ν • λλ Wavelength Meters λ = V • Tλ Wavelength Meters λ = V / νT Period Seconds T = λ / Vν Frequency Hertz ν = V / λ
Chapter 17.2 Properties of Mechanical Waves
8. Math Skills on page 506List, formula, substitution, work, answer9. Math Practice on page 5064.0 m/s0.4 m/s50 cm/s.5 Km10. Math Practice on page 5074.0 m/s.5 s
Chapter 17.3Behavior of WavesA. 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
Chapter 17.3Behavior of WavesB. 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
Chapter 17.3Behavior of WavesC. 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
Chapter 17.3Behavior of WavesD. 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 InterferenceDestructive Interference
INTERFERENCE
Chapter 17.3Behavior of WavesD. INTERFERENCE
Constructive Interference
It occurs when two or more waves combine to produce a wave with a larger displacement.
CONSTRUCTIVEINTERFERENCE
Chapter 17.3Behavior of WavesD. INTERFERENCE
Destructive Interference
It occurs when two or waves combine to produce a wave with a smaller displacements
DESTRUCTIVEINTERFERENCE
Chapter 17.3Behavior of WavesE. 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
Chapter 17.3Behavior of WavesE. 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
Chapter 17.4Sound and HearingA. 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
Chapter 17.4Sound and HearingSPEED 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 SOUNDMedium (at 1 atm) Speed
(m/s)Dry air, 0°C 331Dry air, 20°C 342Fresh water, 0°C 1401Fresh water, 30°C 1509Salt water, 0°C 1449Salt water, 30°C 1546Lead, 25°C 1210Cast iron, 25°C 4480Aluminum, 25°C 5000Borosilicate glass, 25°C
5170
Chapter 17.4Sound and HearingA. 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
Chapter 17.4Sound and HearingA. 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
Sound DecibelThreshold 0Whisper 15-20Normal 40-50
Street noise 60-70Inside a bus 90-100
Heavy machinery
80-120
Rock concert 110-120Pain 120
Jet taking off 120-160
Chapter 17.4Sound and HearingA. 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
Chapter 17.4Sound and HearingA. PROPERTIES OF
SOUND WAVES8. 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
Chapter 17.4Sound and HearingB. 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
Chapter 17.4Sound and HearingB. 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
Chapter 17.4Sound and HearingB. 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
Chapter 17.4Sound and HearingD. THE DOPPLER EFFECT12. 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.
Chapter 17.4Sound and Hearing
Diagram of Doppler Effect14. 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?
Chapter 17.4Sound and HearingE. HEARING AND THE EAR16. 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.
Chapter 17.4Sound and Hearing
The Anatomy of the earFigure 19Page 517
Chapter 17.4Sound and HearingF. 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.
Chapter 17.4Sound and HearingG. 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.
Chapter 17.4Sound and HearingG. 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
Chapter 17Mechanical Waves and Sound
END OF THE CHAPTER
Complete the study guide!
YOUR TEST IS NEXT!