Slide 1 / 144 Slide 2 / 144 8th Grade Wave Properties 2015-10-28 www.njctl.org Slide 3 / 144 Table of Contents: Wave properties What are waves? · Click on the topic to go to that section Parts of a Wave · The Wave Equation · Properties of Waves · Sound as a Wave · Sound as a Mechanical Wave · Properties of Sound Waves · The Doppler Effect ·
Slide 4 / 144 What are Waves? Return to Table of Contents Slide 5 / 144 What is a Wave? A wave is a disturbance that travels through space or matter. What do you notice about the movement of this water? In a wave, what is actually "waving"? Slide 6 / 144 What causes a wave to form? When undisturbed, the water is found in its equilibrium or rest position.
Slide 7 / 144 What causes a wave to form? All waves start by a disturbance in the space or matter they travel through. This wave starts when the water particles are disturbed and move away from the rest position. They want to "bounce back" to the rest position. This disturbance moves outward in all directions. Slide 8 / 144 Pulses vs. Waves A wave is a series of pulses that A pulse is a single produces repeating and periodic disturbance that disturbances in the medium. moves outward. Click here to see a video on pulses and waves Slide 9 / 144 Wave Medium Mechanical waves are waves that travel through matter. The type of matter the wave travels through is called a medium. A medium can be any solid, liquid, or gas. What medium is this wave traveling through?
Slide 10 / 144 Making Waves Click here to see a PhET wave simulation Experiment with different ways to start a wave. Decrease the "damping" and observe what happens to the wave motion. Observe the movement of the green beads in the rope. Slide 11 / 144 1 In the PhET simulation, what medium was the wave traveling through? A Empty space B Air C A rope made up of green and red beads D Water Slide 11 (Answer) / 144 1 In the PhET simulation, what medium was the wave traveling through? A Empty space B Air Answer C C A rope made up of green and red beads D Water [This object is a pull tab]
Slide 12 / 144 2 A pulse is a single disturbance that travels through a medium. True False Slide 12 (Answer) / 144 2 A pulse is a single disturbance that travels through a medium. True False Answer True [This object is a pull tab] Slide 13 / 144 3 Which of the following is the best way to start a wave and keep it going in the simulation? A Give it one manual pulse B Select oscillation C Give it one automatic pulse
Slide 13 (Answer) / 144 3 Which of the following is the best way to start a wave and keep it going in the simulation? A Give it one manual pulse B Select oscillation Answer C Give it one automatic pulse B [This object is a pull tab] Slide 14 / 144 4 Based on the simulation, which of the following is the best definition of the word oscillate ? A To move or travel back and forth B To move or travel randomly C To move or travel in one direction D To move or travel in one abrupt motion Slide 14 (Answer) / 144 4 Based on the simulation, which of the following is the best definition of the word oscillate ? A To move or travel back and forth B To move or travel randomly Answer A C To move or travel in one direction D To move or travel in one abrupt motion [This object is a pull tab]
Slide 15 / 144 5 In the simulation, how would you describe the movement of the green beads in the rope as it was waving? A As the wave moved, the green beads moved forward towards the end of the rope. B As the wave moved, the green beads bounced up and down but did not move forward or backward. C The green beads moved forward with the wave. D The green beads moved backward as the wave moved forward. Slide 15 (Answer) / 144 5 In the simulation, how would you describe the movement of the green beads in the rope as it was waving? A As the wave moved, the green beads moved forward towards the end of Answer B the rope. B As the wave moved, the green beads bounced up and down but did not move forward or backward. [This object is a pull tab] C The green beads moved forward with the wave. D The green beads moved backward as the wave moved forward. Slide 16 / 144 Waves transfer energy and not matter! As energy moves through a medium in the form of a wave, the particles in the medium vibrate around their rest position. Is the medium moving across or up and down? If there were no waves, where would the colored balls be?
Slide 17 / 144 Transverse Waves This wave is classified as a TRANSVERSE WAVE The particles in a TRANSVERSE WAVE vibrate at right angles to the direction of energy movement. Particles move up and down Energy moves right to left Slide 18 / 144 6 The substance that a mechanical wave moves through is called a(n): vacuum A medium B propagation C amplitude D Slide 18 (Answer) / 144 6 The substance that a mechanical wave moves through is called a(n): vacuum A medium B Answer B propagation C amplitude [This object is a pull D tab]
Slide 19 / 144 7 The resting position of a medium when there is NO wave passing through it is known as: Amplitude A Inertia B Minimum Displacement C Equilibrium Position D Slide 19 (Answer) / 144 7 The resting position of a medium when there is NO wave passing through it is known as: Amplitude A Answer D Inertia B Minimum Displacement C [This object is a pull tab] Equilibrium Position D Slide 20 / 144 8 Which of the following is an example of a wave medium? Air molecules and other gases A Water B A slinky C All of the above D
Slide 20 (Answer) / 144 8 Which of the following is an example of a wave medium? Air molecules and other gases A Water B A slinky Answer D C All of the above D [This object is a pull tab] Slide 21 / 144 9 The particles in a transverse wave vibrate at a right angle to the direction of wave motion. True False Slide 21 (Answer) / 144 9 The particles in a transverse wave vibrate at a right angle to the direction of wave motion. True False Answer True [This object is a pull tab]
Slide 22 / 144 10 Waves transfer __________. Matter A Energy B Energy and Matter C Objects from one medium to another D Slide 22 (Answer) / 144 10 Waves transfer __________. Matter A Energy B Energy and Matter C Answer B Objects from one medium to another D [This object is a pull tab] Slide 23 / 144 Parts of a Wave Return to Table of Contents
Slide 24 / 144 The Anatomy of a Wave Let's look at the parts of a wave using a transverse wave in a rope as shown below. Do you remember what classifies a wave as transverse? Slide 25 / 144 The Anatomy of a Wave --------- marks the equilibrium/rest position. This is the position the rope would have if there was no disturbance through it. Once a disturbance is added, the rope will vibrate up and down around this equilibrium position. Slide 26 / 144 The Anatomy of a Wave The Crest (C) of a wave is the point on the medium that exhibits the maximum amount of upward (or positive) displacement from the equilibrium position. C C C
Slide 27 / 144 The Anatomy of a Wave The Trough (T) of a wave is the point on the medium that exhibits the maximum amount of downward (or negative) displacement from the equilibrium position. T T Slide 28 / 144 The Anatomy of a Wave The amplitude (y) of a wave is the maximum distance away from the rest position. It can be measured from the equilibrium position to the crest or to the trough. What are some units that could be used to measure a wave's amplitude? Slide 29 / 144 The Anatomy of a Wave The amplitude (y) of a wave is related to the energy the wave transports. Which of the following waves do you think transports more energy and why?
Slide 29 (Answer) / 144 The Anatomy of a Wave The amplitude (y) of a wave is related to the energy the wave transports. Which of the following waves do you think transports more energy and why? Answer The one on the right transports more energy because it has a larger amplitude. [This object is a pull tab] Slide 30 / 144 The Anatomy of a Wave The energy that a wave transports is directly proportional the square of the wave's amplitude (y). Energy Amplitude 2 This means that if the wave amplitude doubles , the energy the wave transports will quadruple. Can you determine the missing value in the chart below? Amplitude Energy 1 unit 2 units 2 units 8 units 3 units 18 units 4 units Slide 31 / 144 Wavelength Wavelength ( ) is defined as the distance it takes a wave to complete one complete up and down motion or vibration (one complete wave cycle). It can be measured in various places along the wave. What units could be used to measure the wavelength of a wave?
Slide 32 / 144 Wavelength Label the following wavelengths by dragging the arrow line. From Crest to Crest From Trough to Trough From Starting Point to Ending Point along the Equilibrium Position. Slide 33 / 144 11 The distance for a wave to repeat one complete vibration/cycle is called: Trough A Crest B Wavelength C Amplitude D Slide 33 (Answer) / 144 11 The distance for a wave to repeat one complete vibration/cycle is called: Trough A Crest B Wavelength C Answer C Amplitude D [This object is a pull tab]
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