Video lecture for today: https://youtu.be/SvWrMimhP9g
Essential Question: What is a wave?
Goals: SWBAT...
1. Discuss waves’ properties using common vocabulary and they will be able to predict the behavior of waves
2. Describe how changing one characteristic of a wave affect the other characteristics.
Warm-Up (5min):
1. When waves reach the end the material thru which they're traveling, they get reflected. What does "reflected" mean?
2. What is the difference between a wave reflected off a fixed end vs. a loose end?
Waves on a String: https://phet.colorado.edu/en/simulation/wave-on-a-string
CLASSWORK
1. 142A: Guided Reading: Waves
Your own copy is on Schoology
Reading Materials: LINK
2. 142B: "What is a Wave?" Reading/Notes
The link to the reading is below. While reading, define the terms listed, or answer the questions I've given.
What is a Wave?
a. To introduce a wave to a slinky, what must you do to the first coil in the slinky? (hint, there are four options - list them all)
b. Define "wave" (see end of second paragraph)
c. What is the difference between a pulse and a wave?
What is a Medium?
d. Define "medium"
e. How is the function of the wave medium (to carry the wave) similar to the function of the news media, or of a conducting piece of metal?
f. What is the medium of a stadium wave?
Particle-to Particle interaction
g. In a wave, if the first particle (in a slinky, this would be the first coil) is disturbed upwards, what would happen to the second (next) coil?
A Wave Transports Energy, not Matter
h. In the stadium wave, what happens to the particles (the fans) after the wave passes? How is this similar to a water wave?
i. "energy transport phenomenon" In a slinky wave, how does energy get transferred from the first coil to the last?
Link to reading is here ----> LINK
3. What is a standing wave? Set your sim to Oscillate, No End, Amp: 0.67cm, Freq: 1.53, Damping: none, Tension: Medium and see if you can make one.
1. The speed of sound in solid iron is 5,120 m/s. How long would it take a sound wave to travel through 40,075,000 m of iron?
2. Could a sound wave travel that far?
CLASSWORK
1. 10 minutes for work time/questions on our Changing Pitch Lab
2. 142A:
Lab – Tuning Forks and Waves
Purpose – make observation about the waves formed by a tuning fork
You will complete this activity in your notebook. Due Tuesday, at beginning of class.
Pre-lab Question
The speed of sound in room temperature air is approximately 346 m/s. Calculate the wavelength of a sound wave that has a frequency of 500 Hz.
Instructions, Observations, and Calculations
You will need two tuning forks (one high and one low), a binder (or short stack of paper to strike the tuning fork on) and a cup with water to complete the observations.
write down the two frequencies of your tuning forks. They can be found stamped on the fork.
Strike each tuning fork on the paper. Compare the sounds that the tuning forks make and write one observation.
Observe the tuning fork vibrations with your eyes. Write one observation about what you see.
Strike the tuning fork and have it touch your ear and nose. Write one observation about what you feel.
Strike a tuning fork and place it in a cup of water. Write one observation about what you see.
Calculate the wavelength of the tuning fork using the speed of sound given in Pre-Lab question #1 and the frequency on the tuning forks.
Conclusion Questions
Why does sound travel faster when the air is warmer than when it's colder? Think: how could you use the concept of how particles interact in longitudinal sound wave to help explain your answer. Feel free to use the internet to help find your answer
Which tuning fork has a higher pitch? How do you know?
Which turning fork (long or short) has a lower frequency? What about that forks shape forces it to have a lower frequency?
Compare and contrast the low frequency and high frequency tuning forks using a Venn Diagram
How could you increase the intensity of the sound waves you produced using tuning forks?
ECHO PRACTICE: Bats can use echo location to navigate and find prey. If a bat emits a sound then hears it 0.02 seconds later, how far away is the object?
For S.A., and anyone else who has trouble accessing the Google Doc
Guided Reading: Vibrations and Waves
Name: Date: Period:
Start on page 372, “Vibrations and Waves” and answer the following questions as you read:
1. Define a wave:
2. ____________ and _____________ are both forms of energy that move through space as waves.
Continue on to §25.1 “Vibration of a Pendulum” and answer the following questions as you read:
3. _________________ swing back and forth with such regularity that they have long been used to control the motion of ___________.
4. Refer to Figure 25.1, what does the caption read?
5. Define period (of a pendulum):
6. A long pendulum has a _____________ period than a shorter pendulum; that is, it swings back and forth more slowly – ___________ _________________ – than a short pendulum. In much the same way that a person with long legs tends to walk with a ________________ __________ than a person with short legs.
Continue on to page 373, §25.2 “Wave Description” and answer the following questions as you read:
7. Define simple harmonic motion:
8. Refer to Figure 25.2, it reads: Frank Oppenheimer, founder of the Exploratorium® science museum in San Francisco, demonstrates that a _________________ swinging back and forth traces out a ___________________ ___________ over a stationary surface, and a _________ ____________ when the surface moves at a constant speed.
9. A sine curve is a pictorial representation of a ____________.
10. Like a water wave, the high points are called ______________, and the low points are called ______________.
11. The straight dashed line represents the “____________” position, or midpoint of the vibration.
12. The term ________________ refers to the distance from the ________________ to the crest (or trough) of the wave. So the amplitude equals the maximum _________________________ from equilibrium.
13. Define wavelength:
14. Or equivalently, the wavelength is the distance between successive ______________ ________ of the wave.
15. Define frequency:
16. The frequency of a vibrating pendulum, or object on a spring, specifies the number of back and forth vibrations it makes in a ____________ __________ (usually _________ _____________).
17. A complete back and forth vibration is one __________. If it occurs in one second, the _________________ is one vibration per second or one cycle per second.
18. The unit of frequency is called the ____________ (______). A frequency of one __________ per second is 1 hertz, two cycles per second is 2 ___________, and so on.
19. Higher frequencies are measured in ________________ (_______– thousands of hertz), and still higher frequencies in _________________ (_______– millions of hertz) or _________________ (_______– billions of hertz).
20. The source of all waves is something that ________________. The frequency of the vibrating source and the __________________ of the wave it produces are the same.
21. If the frequency of a vibrating object is known, its _______________ can be calculated, and vice versa.
22. What is the equation for frequency in terms of period:
23. And vice versa, what is the equation for period in terms of frequency:
Continue on to page 375, §25.3 “Wave Motion” and answer the following questions as you read:
24. Most of the information around us gets to us in some form of wave. ______________ is energy that travels to our ears in the form of one kind of wave. _______________ is energy that comes to our eyes in the form of a different kind of wave (an ________________________ ________.
25. When energy is transferred by a wave from a vibrating ____________ to a distant
______________, there is no transfer of ______________ between the two points.
26. Refer to Figure 25.5, what does the caption read?
27. The energy transferred from a vibrating source to a receiver is carried by a _________________________ in a medium, not by ___________ moving from one place to another within the ________________.
Continue on to page 376, §25.4 “Wave Speed” and answer the following questions as you read:
28. The speed of a wave depends on the ________________ through which the wave moves. Sound waves, for example, move at speeds of about ___________m/s to ___________m/s in air (depending on temperature), and about _____________ times faster in water.
29. Whatever the medium, the ____________, the __________________, and _________________ of the wave are related.
30. In words, what is the equation for wave speed in terms of wavelength and frequency?
31. What is it in equation form?
32. In this equation, ν is __________ ______________, λ (Greek letter lambda) is ____________________, and f is __________ __________________.
33. This relationship holds for all kinds of ____________, whether they are water waves, sound waves, radio waves, or light waves.
34. Refer to Table 25.1: Sounds Waves, what is the wavelength (m) of a wave that has a wave speed of 340 m/s and a frequency of 396 Hz? _____________
35. Refer again to Table 25.1, notice that long wavelengths have ________ frequencies, and short wavelengths have __________ frequencies. Wavelength and frequency vary ________________ to produce the same wave speed for all sounds.
Continue on to page 378, §25.5 “Transverse Wave” and answer the following questions as you read:
36. When you create a wave by shaking a rope up and down, as shown in Figure 25.8, the motion of the rope (shown by the up and down arrows) is at __________ _____________ to the direction in which the wave is moving.
37. Whenever the motion of the ______________ (the rope in this case) is at right angles to the direction in which a wave travels, the wave is a ____________________ _____________.
38. Waves in the stretched ______________ of musical instruments and upon the surfaces of liquids are ____________________. As Chapter 27 will show, the electromagnetic waves that make up ________________ ____________ and ________________ are also transverse.
Continue on to page 378, §25.6 “Longitudinal Wave” and answer the following questions as you read:
39. Not all waves are _________________. Sometimes the particles of the medium move back and forth in the same direction in which the _____________ travels.
40. The particles move __________ the direction of the wave rather than at right angles to it. This kind of wave is a ___________________________ wave.
41. Other than the Slinky®, what other example for a longitudinal wave does the author mention?