2Unit 3: Energy On the Move Table of Contents10Unit 3: Energy On the MoveChapter 10: Waves10.1: The Nature of Waves10.2: Wave Properties10.3: The Behavior of Waves
3The Nature of Waves10.1What’s in a wave?wave is a repeating disturbance or movement that transfers energy through matter or space.Examples?
4The Nature of Waves10.1Waves and EnergyClick image to view movie
5The Nature of Waves10.1Waves and EnergyBecause it is moving, the falling pebble has energy.As it splashes into the pool, the pebble transfers some of its energy to nearby water molecules, causing them to move.What you see is energy traveling in the form of a wave on the surface of the water.
6Waves and Matter 10.1 Imagine you’re in a boat on a lake. The Nature of Waves10.1Waves and MatterImagine you’re in a boat on a lake.Approaching waves bump against your boat, but they don’t carry it along with them as they pass.
7The Nature of Waves10.1Waves and MatterThe waves don’t even carry the water along with them. Only the energy carried by the waves moves forward.All waves have this propertythey carry energy without transporting matter from place to place.
8The Nature of Waves10.1Making WavesA wave will travel only as long as it has energy to carry.
10The Nature of Waves10.1Making WavesIt is the up-and-down motion of your hand that creates the wave.Anything that moves up and down or back and forth in a rhythmic way is vibrating.The vibrating movement of your hand at the end of the rope created the wave. In fact,-All waves are produced by something that vibrates.
11The Nature of Waves10.1Mechanical WavesMedium- matter the waves travel through is called a The medium can be a solid, a liquid, or gas
12The Nature of Waves10.1Mechanical Wavesmechanical waves- Waves that can travel only through a medium.Not all waves need a medium.Light and radio waves, can travel through space. (No Medium)The two types of mechanical waves are transverse waves and compressional waves.
13The Nature of Waves10.1Transverse Wavestransverse wave, Waves move at right angles to the direction that the wave travels. (Like water waves)For example, a water wave travels horizontally as the water moves vertically up and down.
14The Nature of Waves10.1Compressional Wavescompressional wave, waves move the same direction that the wave travels.You can model compressional waves with a coiled spring toy.
15The Nature of Waves10.1Compressional WavesSqueeze several coils together at one end of the spring. Then let go of the coils.
16The Nature of Waves10.1Compressional WavesAs the wave moves, it looks as if the whole spring is moving toward one end.The wave carries energy, but not matter, forward along the spring.Compressional waves also are called longitudinal waves.
17Sound Waves 10.1 Sound waves are compressional waves. The Nature of Waves10.1Sound WavesSound waves are compressional waves.When a noise is made, such as when a locker door slams shut and vibrates, nearby air molecules are pushed together by the vibrations.
18The Nature of Waves10.1Sound WavesThe air molecules are squeezed together like the coils in a coiled spring toy are when you make a compressional wave with it.The compressions travel through the air to make a wave.
19Sound in Other Materials The Nature of Waves10.1Sound in Other MaterialsSound waves also can travel through other mediums, such as water and wood.When a sound wave reaches your ear, it causes your eardrum to vibrate.Your inner ear then sends signals to your brain, and your brain interprets the signals as sound.
20The Nature of Waves10.1Water WavesOcean waves are formed most often by wind blowing across the ocean surface.The size of the waves that are formed depend on the wind speed, the distance over which the wind blows, and how long the wind blows.
21The Nature of Waves10.1Seismic WavesForces in Earth’s crust can cause regions of the crust to shift, bend, or even break.The breaking crust vibrates, creating seismic (SIZE mihk) waves that carry energy outward.
22The Nature of Waves10.1Seismic WavesSeismic waves are a combination of compressional and transverse waves. They can travel through Earth and along Earth’s surface.The more the crust moves during an earthquake, the more energy is released.Click image to view movie
23Question 1 Answer 10.1 What is a wave? Section Check10.1Question 1What is a wave?AnswerA wave is a repeating movement that transfers energy through matter or space.
24Question 2 10.1 Which is carried by a water wave? Section Check10.1Question 2Which is carried by a water wave?A. a boat on the surfaceB. boat anchor submerged 50 mC. energyD. water molecules
25Section Check10.1AnswerThe answer is C. Waves carry energy without transporting matter from place to place.
26Question 3 10.1 Which type of wave does not need a medium? Section Check10.1Question 3Which type of wave does not need a medium?A. electromagneticB. mechanicalC. oceanD. sound
27Section Check10.1AnswerThe answer is A. Electromagnetic waves are made by vibrating electric charges and can travel through space where matter is not present.
28Wave Properties10.2The Parts of a WaveWaves can differ in how much energy they carry and in how fast they travel.Waves also have other characteristics that make them different from each other.
29The Parts of a Wave 10.2 crests - Alternating high points Wave Properties10.2The Parts of a Wavecrests - Alternating high pointstroughs - Alternating low points
30The Parts of a Wave 10.2 Parts of a compressional wave Wave Properties10.2The Parts of a WaveParts of a compressional waveCompression- region where the coils are close together.
31Wave Properties10.2The Parts of a WaveRarefaction- region where coils are spread apart
32Wave Properties10.2Wavelengthwavelength is the distance between two of the same points on a wave
34Wave Properties10.2WavelengthThe wavelengths of sound waves that you can hear range from a few centimeters for the highest-pitched sounds to about 15 m for the deepest sounds.
35Wave Properties10.2Frequency and Periodfrequency of a wave is the number of wavelengths that pass a fixed point each second.transverse waves- number of crests that pass by a point each second.Frequency is expressed in hertz (Hz).
36Wave Properties10.2Frequency and PeriodPeriod- amount of time it takes one wavelength to pass a point.
37Wavelength is Related to Frequency Wave Properties10.2Wavelength is Related to FrequencyAs frequency increases, wavelength decreases.If you move the rope up, down, and back up in 1 s, the frequency of the wave you generate is 1 Hz.
38Wave Properties10.2Sound and MediumsSound travel faster in liquids and solids than they do in gases.Light waves travel more slowly in liquid and solids than they do in gases or in empty space.Sound waves faster in a material if the temperature of the material is increased.
39Calculating Wave Speed Wave Properties10.2Calculating Wave SpeedYou can calculate the speed of a wave represented by v by multiplying its frequency times its wavelength.
40Amplitude and Energy 10.2 Amplitude energy carried by a wave. Wave Properties10.2Amplitude and EnergyAmplitude energy carried by a wave.The greater the wave’s amplitude is, the more energy the wave carries.Click image to play movie
41Amplitude of Compressional Waves Wave Properties10.2Amplitude of Compressional WavesThe closer the coils are in a compression, the farther apart they are in a rarefaction.
42Amplitude of Transverse Waves Wave Properties10.2Amplitude of Transverse WavesDraw Picture
43Section Check10.2Question 1If a wave has a high point and a low point, is it a compressional or transverse wave?
44Section Check10.2AnswerTransverse waves have alternating high points, called crests, and low points, called troughs.
45Section Check10.2Question 2What is the wavelength of a wave?
46Section Check10.2AnswerA wavelength is the distance between one point on a wave and the nearest point just like it.
47Section Check10.2Question 3Which of the following refers to the number of wavelengths that pass a fixed point each second?A. frequencyB. periodC. wavelengthD. wave speed
48Section Check10.2AnswerThe answer is A. Period is a length of time, and wavelength is a distance.
49To Be a Wave 10.3 All waves must- Reflect, Refract, and Diffract. The Behavior of Waves10.3To Be a WaveAll waves must- Reflect, Refract, and Diffract.
50Reflection 10.3 What about Sound Waves The Behavior of Waves10.3ReflectionHow does the reflection of light allow you to see yourself in the mirror? It happens in two steps. First, light strikes your face and bounces off. Then, the light reflected off your face strikes the mirror and is reflected into your eyes.What about Sound Waves
51The Behavior of Waves10.3EchoesEcho - sound waves hit an object, they reflect and come back to you. You hear the sound multiple times.
52The Law of Reflection 10.3 Draw this Picture: The Behavior of Waves10.3The Law of ReflectionDraw this Picture:The beam striking the mirror is called the incident beam.The beam that bounces off the mirror is called the reflected beam.
53The Behavior of Waves10.3The Law of ReflectionThe line drawn perpendicular to the surface of the mirror is called the normal.
54The Behavior of Waves10.3The Law of ReflectionThe angle formed by the incident beam and the normal is the angle of incidence.The angle formed by the reflected beam and the normal is the angle of refection.
55The Behavior of Waves10.3The Law of Reflectionlaw of reflection- The angle of incidence is equal to the angle of refection.All reflected waves obey this law.
56The Behavior of Waves10.3RefractionWhen a wave passes from one medium to another. It changes speed and direction. (Example: from air to water)If the wave is traveling at an angle when it passes from one medium to another, it changes direction, or bends, as it changes speed.
57The Behavior of Waves10.3RefractionRefraction- Bending of a wave caused by a change in its speed as it moves from one medium to another.
58Refraction of Light in Water The Behavior of Waves10.3Refraction of Light in WaterLight waves travel slower in water than in air. This causes light waves to change direction and bend toward the normalWhen light waves travel from air to water, they slow down and bend toward the normal.
59Refraction of Light in Water The Behavior of Waves10.3Refraction of Light in WaterYou may have noticed that objects that are underwater seem closer to the surface than they really are.In the figure, the light waves reflected from the swimmer’s foot are refracted away from the normal and enter your eyes.
60Refraction of Light in Water The Behavior of Waves10.3Refraction of Light in WaterHowever, your brain assumes that all light waves have traveled in a straight line.The light waves that enter your eyes seem to have come from a foot that was higher in the water.
61The Behavior of Waves10.3DiffractionWhen waves strike an object, several things can happen.The waves can bounce off, or be reflected.If the object is transparent, light waves can be refracted as they pass through it.Waves also can behave another way when they strike an object. The waves can bend around the object.
62The Behavior of Waves10.3DiffractionDiffraction - an object causes a wave to change direction and bend around it.Diffraction and refraction both cause waves to bend. The difference is that refraction occurs when waves pass through an object, while diffraction occurs when waves pass around an object.
63The Behavior of Waves10.3DiffractionAfter they pass through the opening, the waves spread out.
64Diffraction and Wavelength The Behavior of Waves10.3Diffraction and WavelengthExamples of diffraction?
65Hearing Around Corners The Behavior of Waves10.3Hearing Around CornersLight waves have a much shorter wavelength. They are hardly diffracted at all by the door.
66Diffraction of Radio Waves The Behavior of Waves10.3Diffraction of Radio WavesAM radio waves have longer wavelengths than FM radio waves do. Because of their longer wavelengths, AM radio waves diffract around obstacles like buildings and mountains.As a result, AM radio reception is often better than FM reception around tall buildings and natural barriers such as hills.
67The Behavior of Waves10.3Interferenceinterference When two or more waves overlap and combine to form a new wave
68Constructive Interference The Behavior of Waves10.3Constructive Interferenceconstructive interference- waves add together.
69Constructive Interference The Behavior of Waves10.3Constructive Interference
70Destructive Interference The Behavior of Waves10.3Destructive Interferencedestructive interference- waves cancel each other.
71The Behavior of Waves10.3Standing Wavesstanding wave - waves equal in wavelength and amplitude, travel in opposite directions, and interfere with each other.
72Standing Waves in Music The Behavior of Waves10.3Standing Waves in MusicWhen the string of a violin is played with a bow, it vibrates and creates standing waves.Some instruments, like flutes, create standing waves in a column of air.
73The Behavior of Waves10.3Resonanceresonance - object is made to vibrate by absorbing energy at its natural frequencyIf enough energy is absorbed, the object can vibrate so strongly that it breaks apart.
74Question 1 Answer 10.3 State the law of reflection. Section Check10.3Question 1State the law of reflection.AnswerAccording to the law of reflection, the angle of incidence is equal to the angle of reflection.
75Section Check10.3Question 2__________ is the bending of a wave caused by a change in its speed as it moves from one medium to another.A. diffractionB. diffusionC. refractionD. reflection
76Section Check10.3AnswerThe answer is C. The greater the change in speed is, the more the wave bends.
77Section Check10.3Question 3Which is the means by which you can hear around corners?A. diffractionB. diffusionC. reflectionD. refraction
78Section Check10.3AnswerThe answer is A. Diffraction occurs when an object causes a wave to change direction and bend around it.
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