What are the characteristics of a transverse wave?

Transcription

1 Guiding Question What are the characteristics of a transverse wave? 1

2 Key Vocabulary Key Vocabulary } amplitude } frequency } function } longitudinal } transverse } structure } wavelength 2

3 Get Started Modeling waves with a spring } Scientists and engineers create models to show how thinks work, to describe and explain why things happen, and to make predictions. 3

4 Introduction Read the introduction and look for key ideas 4

5 Get Started Venn diagram 5

6 Do the Activity Safety } Handle the springs with care and never let go suddenly when the spring is under tension. If released when tension is being applied, the spring can move rapidly and unpredictably and could scratch someone. Wear safety goggles to protect your eyes from such an event. 6

7 Do the Activity Teacher demonstration 7

8 Do the Activity Complete procedure part A: Wave Pulses } Record your data in your notebook. 8

9 Do the Activity Did 100% of the energy that you put into the pulse make it to the end of the spring? } Share your thoughts with the class. 9

10 Do the Activity Complete procedure part B: Transverse } Record your data in your notebook. 10

11 Do the Activity Interpreting Graphs 11

12 Do the Activity Interpreting Graphs 12

13 Do the Activity Relationship between variables } proportion } graph } mathematical symbols 13

14 Build Understanding Science practices and crosscutting concepts } Used evidence to build knowledge } Patterns 14

15 Analysis Analysis 1 } Describe what happened when a. the wave pulses reached the end of the spring. b. the transverse wave reached the end of the spring. a. the wave pulses reached the end of the spring. The pulses reflected off the fixed end on the opposite side. b. the transverse wave reached the end of the spring. Both sides of the wave reflected onto the opposite sides, like with the pulse, but they did so simultaneously so it looked like the top and bottom of the wave switched sides when reflected. 15

16 Analysis Analysis 2 } What happened when the spring was stretched to double its length?. The wave traveled faster and its amplitude decreased. 16

17 Analysis Analysis 3 } What happened to the amplitude of the wave pulse when it traveled along the spring? Suggest an explanation for your observations.. The wave pulse got smaller and, therefore, its amplitude must have decreased.this is probably because the wave used some of its energy to overcome friction as it moved across the surface of the floor. 17

18 Analysis Analysis 4 } Do you think that sound also has a wavelength? Explain why or why not. Sound must have a wavelength. because it has a frequency, and they go together. Since a wavelength is the distance of one cycle, I think the wavelength is the distance between compressions. 18

19 Analysis Analysis 5 } Look at the diagram shown on the right of a wave made with a spring. a. Describe the motion of the spring at points B and C. a. Describe the motion of the spring at points B and C. The motion of the spring at B is up and down from the maximum height to minimum height.the spring at position C moves up and down but does so at a slightly later time than the spring at position B. 19

20 Analysis Analysis 5 continued } Look at the diagram shown on the right of a wave made with a spring. b. Is the energy transfer of the wave parallel or perpendicular to the motion of the spring at point B? Explain.. Is the energy transfer of the wave parallel or perpendicular to the motion of the spring at Point B? Explain. The energy transfer is from end to end, or between points A and D. The motion of the spring at part B is up and down, which is perpendicular to the energy transfer. 20

21 Analysis Analysis 6 } Trace the diagram from the previous question above, and then a. draw what the wave would look like if the amplitude was doubled. b. draw what the wave would look like if the frequency was doubled. c. draw what the wave would look like if the wavelength was doubled. Show page 73 from teacher s notebook. 21

22 Analysis Analysis 7 } Make two tables like the ones shown, and fill in the missing diagrams to show changes in wavelength and frequency. Then explain what your diagrams model. } Show answer from teacher s book page 74 22

23 Analysis Analysis 8 } For a wave of a given speed, what is the relationship between the wavelength and the frequency? Use your diagrams from the activity and the model from the previous item to look for patterns.. As the wavelength of a wave increases, if everything else is constant, the frequency will decrease.when the wavelength decreases, the frequency increases. 23

24 Analysis Analysis 9 } A transverse wave with constant speed has an increase in amplitude over time, as shown in the lefthand column of the table shown. Some of the data for energy and wavelength is missing. 24

25 Analysis Analysis 9 continued a. Look at the patterns in the data and predict the missing energies and wavelengths of the wave. In your science notebook, copy the last two rows of the table and complete the data. Then explain the pattern you followed to fill in the data. The pattern is that the energy is equal to the square of the amplitude times 10.The energy is not related to the wavelength or time. 25

26 Analysis Analysis 9 continued b. Make a graph of amplitude (x-axis) vs. energy (y-axis) that includes all five times. Make sure to label your graph. See teacher page 76 d. Use your graph to predict the energy and wavelength for the amplitude of 7 m. For the amplitude of 7m, the energy is 490 J and the wavelength is 0.3 m. 26

27 Analysis Scoring Guide: Organizing Data for Analysis 27

28 Revisit the Guiding Question What are the characteristics of a transverse wave? 28

29 Review Key Vocabulary definitions } amplitude - The maximum displacement of a wave from its state of rest. For a mechanical wave, amplitude can be measured as a distance or a pressure. } frequency - The number of times an event repeats in a given time. For sound it is the number of vibrations per second. 29

30 Review Key Vocabulary definitions } function - A purpose or function which a particular thing can perform. } longitudinal wave - A wave that transfers energy through compressions and rarefactions in the material through which the energy travels. 30

31 Review Key Vocabulary definitions } transverse wave - A wave that consists of vibrations that are perpendicular to the direction that the energy travels. } structure - The way something is formed, built, or organized. } wavelength - The length of one wave cycle. 31

32 Extension Extension } Investigate a standing wave and model them with your long spring. 32