1. Activity 90: The Frequency of Sound Warm up: A. How many decibels is a sound that has a relative intensity of 100,000? B. Label the parts of the wave below: You will need your paper copy of Act. 90 notes!

2. Activity 90: The Frequency of Sound

3. Next Quiz Our next quiz will be on Monday, February 29 th. It will be over everything we have gone over for Unit F. You are allowed to make notes on one side of a 3x5 notecard.

4. Activity 90: The Frequency of Sound What is the word to describe number of vibrations per second that your ear can hear? Frequency! What is the unit that frequencies are measured in? Hertz (Hz), or wave cycles per second.

5. Activity 90: Put this in OneNote or fill- in notes! How can we tell how fast a wave is moving? Speed (m/s)= frequency (Hz) x wavelength (m)

6. Activity 90: The Frequency of Sound Step 1 : tie the string firmly to the washer, making sure at least 30 cm of the string extends from the washer. Step 2 : tie the red yarn firmly to the opposite side of the washer, making sure that 150 cm extends below the washer.

7. Activity 90: The Frequency of Sound Each member of your group has a role. Swinger: holds string high enough that it is not touching the ground; makes sure that the pendulum is swinging at a steady rate. Timer: Times how long it takes to swing the washer 10 complete swings. Measurer: Estimates the length of the wave produced in the yarn. Recorder: Records the data for the group.

8. Frequency Formula Knowing that frequency and wavelength are inversely proportional, what do you think the formula for frequency is? Frequency = speed/ wavelength F= c/λ

9. Frequency Formula F= c/λ What would be the frequency of the values below? C (speed, m/s)λ (m) 12 4.0 14 2.0 3 1.5

10. Frequency Formula F= c/λ What would be the speed of the values below? F (Hz)λ (m).254.0 242.0 6.0

11. Activity 90 Analysis Question Jigsaw Each member of your group will be assigned 1-2 analysis questions. Take a few minutes to answer your question. When all group members are finished, share your answer and record the answers of your groupmates.

12. Activity 90: In Case You Missed It… Amplitude: a wave’s displacement from its state of rest. Wavelength: a measure of one wave cycle. Measured from highest point to highest point or from lowest point to lowest point.

13. Activity 90: In Case You Missed It… The crest is the highest point on a wave, while a trough is the lowest point.

14. Activity 90: In Case You Missed It… Frequency and wavelength are inversely proportional: as one increases, the other decreases.

15. Activity 90 In Case You Missed It…

16. Activity 91: Longitudinal and Transverse Waves Please open your books to page F14.

17. Activity 91: Longitudinal and Transverse Waves

18. What are a few different types of waves, besides sound?

19. Activity 91: Longitudinal and Transverse Waves A longitudinal wave is one that transfers energy through compression and rarefactions in the material that it is travelling. A compression is the region of the wave in which the material through which the wave is transmitted is pressed together.

20. Activity 91: Longitudinal and Transverse Waves A rarefaction is the region in which the material is spread apart.

21. Activity 91: Longitudinal and Transverse Waves A transverse wave does not have compressions and rarefactions. For it to be transmitted through a material, the motion of the material is perpendicular to the direction that the energy travels.

22. Activity 91: Longitudinal and Transverse Waves Focus: How are sound waves similar to, and different from, other types of waves? Looking at your packet, decide what role you want to have first. Record your role as well as a description of it.

23. Activity 91: Longitudinal and Transverse Waves Group Interaction Scoring Guide: When working with your group, you are expected to participate, be respectful, help each other and build on one another’s ideas. Not achieving at least a Level 3 on this scoring guide results in a loss of Life Skills points.

24. Activity 91: Longitudinal and Transverse Waves Follow the procedure in your packet, not your book! Stick to your role, but when it is time, be sure to switch. All group members should have data and diagrams by the end.

25. Tonight’s Homework Complete the analysis questions in your packet, not in OneNote. Act. 91 UC assessment due on Monday, Feb. 29 th ! Quiz on Monday, Feb. 29 th !