2. Vocabulary Vibration – A wiggle in an amount of time. Period – The time of a back and forth swing in a pendulum. Wave – A wiggle in space and time. Must extend from one place to another.

3. Vocab cont. Wavelength Crest Trough

4. Vocab cont (again) Amplitude – Mid-point to crest

5. Vocab (even more) Frequency – How often a vibration occurs.

6. Vocab (I know, I know) Hertz (Hz) – Unit for frequency. 1 Hz is one cycle per second. 2 Hz is two cycles per second.

7. Formulas Frequency = 1/period Period = 1 vibration/frequency

8. Example 1 What is the frequency in vibrations per second of a 100-Hz wave? Answer: 100 times per second

9. Example 2 The Sears Building in Chicago sways back and forth at a frequency of about 0.1 Hz. What is its period of vibration?

10. Answer Period = 1 vibration Frequency Period = 1 vibration = 1 vibration 0.1 Hz 0.1 vibration/second Period = 10 s

11. Waves Get into groups of 5 Calculate – write these in your notes and take book with you. Amplitude – Beginning and ending Wavelength Frequency Distance from Crest to Trough *Have patience, we are sharing one cord.