1. PS 1-3-08 Waves and Sound

2. New Website address www.Elyceum.wikispaces.com

3. Time until exams About a week of class time towards new material Waves, sound, light, and maybe color Some graded exercise on next Wednesday

4. Mid-year exam Review next Thursday and Friday Find your old tests

5. Waves Interference Constructive interference Destructive interference

6. Relationship between type of interference and amplitude size

7. Interference and bubbles Constructive and destructive interference creates rainbow effect on bubbles

8. Interference and sound Keeping a piano in tune Dead Spots in a room

9. Standing waves Occurs where at least one end of wave is fixed Relationship between incoming wave and reflected wave

11. Standing waves in guitar

12. Nodes Place along medium of complete destructive interference Crest of incoming cancels trough of reflected (or vice versa)

13. Antinodes Place of maximum vibration Constructive interference

14. Tacoma Narrows Bridge Wind created a standing wave with in structure of bridge

15. Homework Page 478 Problems 1-6

16. Sound Type of wave Speed of Sound 331m/s @ 0°C to 386 @ 25C 1490-1530 C in water 3800-5000 C

17. Loudness Depends on the energy in the sound wave Intensity = rate of energy transmission through a given area of the medium Greater Intensity  Louder sound

18. Measure of Loudness Relative intensity Compares the intensity of the sound with the intensity of the quietest sound that a person can hear Measured in decibels

19. Decibel scale 0 dB  threshold of hearing 30 dB  whispering 50dB  normal conversation 70dB  vacuum cleaner 90 dB  lawnmower 120 dB  threshold of pain 150 dB  nearby jet airplane

21. Pitch Not related to loudness Related to the frequency of wave Humans range of hearing range from –20 HZ to 20,000 HZ

22. Sound beyond human range Lower than 20 Hz  Infrasound Higher than 20,000 Hz  ultrasound Dogs can hear to 46,000 Hz Dolphins can hear to 150,000 Hz

23. Echos What is needed to create an echo?

24. Places you here an echo

25. Ultrasound Ultrasonic waves are generated and moves away from the source They hit an object and reflect back to the source The time it takes for the wave to return is recorded and used to find the distance object is from source D = v t

26. Example of ultrasound use

27. Why use ultrasonic waves? Focused into more narrow beams Directed more easily

28. SONAR Sound, Navigation, and RAnging Uses acoustic signals and echo returns to locate objects