WAVES!!!!
SECTION 1 & 2 WAVES & MECHANICAL WAVES
What is a Wave? A wave is a disturbance that travels through space or matter.
When undisturbed, the water is found in its equilibrium or rest position.
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.
A pulse is a single disturbance that moves outward. Pulses vs. Waves A wave is a series of pulses that produces repeating and periodic disturbances in the medium. Optional video: can fast forward through it Click here to see a video on pulses and waves
Let s Make a Wave! Materials: Bowl with water Object that sinks and one that floats Procedures: Place your finger in the center of the container; observe Place your fist in the center; observe Drop the solid white object; observe Place the floating object and carefully rock the container back and forth, observe Clean up any spills!!
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. Which of the following is an example of a wave medium? A. air molecules and other gases B. water C. a Slinky D. all of the above
Which of the following is an example of a wave medium? A. air molecules and other gases B. water C. a Slinky D. all of the above
Waves through a Medium Practice: workbook p. 25 #4 Which statement best describes how the particles of a medium behave when a mechanical wave moves through the medium? A. Particles travel in the direction of the wave, away from the source of the wave. B. Particles in the medium travel in the direction that is perpendicular to the motion of the wave. C. Particles move as the wave passes them but do not move along the wave. D. Particles stay in one place as the wave travels past them.
Waves through a Medium Practice: workbook p. 25 #4 Which statement best describes how the particles of a medium behave when a mechanical wave moves through the medium? C. Particles move as the wave passes them but do not move along the wave. Waves carry energy, not particles.
Tsunami and Waves Tsunami is a large ocean wave caused by the disturbance in or around the sea. Video: national geographic https://www.youtube.com/watch?v=_opb_9godn4 Time: 2:42
Earthquakes and Waves Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. Video: national geographic https://www.youtube.com/watch?v=e7ho6z32yyo Time: 2:56
Longitudinal Waves A longitudinal wave is when the motion of the medium is parallel to the direction of the wave. This means that the particles move forward and backward which in turn makes the other particles start to oscillate.
Longitudinal Waves - Examples Sound waves are longitudinal waves. Other examples include tsunami waves, earthquake P waves, ultra sounds and oscillations in springs.
Workbook pg. 8 # 6 What does a tsunami have in common with the wave generated by the person jumping into a pool?
ANSWER: Workbook pg. 8 # 6 What does a tsunami have in common with the wave generated by the person jumping into a pool? The person jumping into the pool is like the fault movement that causes the tsunami wave. The waves in the pool and the waves of the tsunami move outward from the disturbance. The greater the distance, the more energy that is transferred, thus the larger the resulting wave.
Transverse Wave A transverse wave is a wave in which the motion of the medium is a right angle to the direction of the wave. The particles vibrate perpendicular or up and down to the direction the wave travels
Longitudinal Vs. Transverse Motion View the pictures and descriptions https://www.acs.psu.edu/drussell/demos/waves/w avemotion.html
The Anatomy of a Wave Let's look at the parts of a wave using a transverse wave in a rope as shown below.
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. When there is a disturbance in a medium and a wave is created, the particles in that medium move away from their rest position. After this occurs, the particles bounce back and return to their rest position.
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
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
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. Amplitude of a wave is related to its height.
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 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? The one on the right transports more energy because it has a larger amplitude.
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. Wavelength is the distance between points on two waves.
What is Frequency? The Frequency (f) of a wave is defined as the number of waves that pass a given point in a set period of time. 1 Vibration per Second (1/sec) is called a Hertz (Hz) The Hertz is the SI unit for measuring frequency of any wave! If a wave vibrates 20 times per second, its frequency is 20 Hz. Frequency deals with the pitch of a object.
Wavelength and Frequency Wavelength and frequency are inversely related to each other. As the period of the wave, T, increases below, what happens to the frequency of vibrations?
Answer Wavelength and Frequency Wavelength and frequency are inversely related to each other. As the period of the wave, T, increases below, what happens to the frequency of vibrations? As period increases, the frequency decreases. As frequency increases, period decreases!
Wave Speed Wave speed is the rate at which a wave travels. Calculated by wavelength x frequency Practice: workbook p. 15 #15 What is the speed of a wave that has a wavelength of 2 m and a frequency of 6 Hz?
Answer p. 15 #15 What is the speed of a wave that has a wavelength of 2 m and a frequency of 6 Hz? Wave speed = wavelength x frequency Wave speed = 2 m x 6 Hz Wave speed = 12 m/s
Amplitude The relationship between amplitude and wave energy is that energy is proportional to amplitude squared. Practice: workbook p. 16 #17 Suppose the energy of a wave increased by a factor of 25. By what factor did the amplitude of the wave increase?
Answer p. 16 #17 Suppose the energy of a wave increased by a factor of 25. By what factor did the amplitude of the wave increase? 5 If the energy increases by a factor of 25, then amplitude increased by a factor of 5 because energy is proportional to the square of the amplitude.
Sound Waves A sound wave is a longitudinal mechanical wave caused by the vibrations of particles as the wave travels through a medium. Since a medium is a solid, liquid or gas sound waves can travel through all of these.
Mechanical waves Mechanical waves spread out through a medium over time. These waves spread out in as many directions as they are able. Workbook pg. 30 #15 How is the energy of the wave changing in this graph and why might this be occurring?
Answer Workbook pg. 30 #15 How is the energy of the wave changing in this graph and why might this be occurring? A, The energy of the wave is related to its amplitude; the lower the amplitude, the less energy a wave has.
Wave Properties Practice Answer the questions on the right and in yellow. http://mathxscience.com/waves.html Click on the question for the correct answer.
Wave Behavior Waves exhibit characteristic behaviors when they interact with boundaries. When a wave hits a boundary, they can be: absorbed reflected transmitted
Wave Absorption As waves travel through any medium, some of its energy is absorbed by the atoms or molecules of the medium. This absorption causes the atoms and molecules to vibrate more creating heat energy. The energy of the wave decreases. Due to friction, some of the wave s energy is transferred into thermal energy. You've probably experienced this when someone is yelling at you from far away. Some of the sound wave is absorbed by the air molecules, so you don't hear them very well.
Workbook p. 31 #16 Whales and dolphins both use sound underwater. Dolphins use high-frequency sounds to locate objects. These waves can travel a few hundred meters. Whales use low-frequency sounds to communicate. These waves can travel hundreds of kilometers. Why might these sounds travel different distances?
ANSWER Workbook p. 31 #16 Whales and dolphins both use sound underwater. Dolphins use high-frequency sounds to locate objects. These waves can travel a few hundred meters. Whales use low-frequency sounds to communicate. These waves can travel hundreds of kilometers. Why might these sounds travel different distances? The rate of absorption may impact the distance the wave s energy travels. High-frequency sounds are absorbed faster than low-frequency sounds.
Reflection When a wave strikes a boundary or an obstacle and bounces back towards the source, the wave and the energy it transports is reflected. Here we see light waves reflected off of water.
Wave Transmission When waves hit a boundary, not all of it is reflected. Some of the wave goes through the new material. This is called wave transmission. The amount of the wave that is reflected and transmitted depends on the type of wave and the medium it hits. Not all of the light waves are reflected from the surface of the water. Some are transmitted through the water down below.
Workbook p. 33 # s 21 & 22 21. What occurs when this wave traveling through the rope encounters a new medium, the wall? 22. How would you best describe the behavior of the wave when it reaches the boundary between the heavy particles and the light particles?
ANSWER Workbook p. 33 # s 21 & 22 21. What occurs when this wave traveling through the rope encounters a new medium, the wall? The wave struck the new medium, and reflects back to the rope. 22. How would you best describe the behavior of the wave when it reaches the boundary between the heavy particles and the light particles? The wave is partly reflected and partly transmitted into the new medium.
Test Sections 1 & 2 Link for Games on the last slide
STOP HERE!!!!!
Games Review Games select a game to review waves information https://reviewgamezone.com/gamelist.php?id=54&name=waves