1. Section 3: Sound and Light
How do dolphins detect objects in murky water?

2. Sound waves are produced by compression and rarefaction of vibrating objects:
Compression: forward movement. Creates regions of high density
Rarefaction: backward movement. Creates region of low density.

3. Sound and Us: We hear frequencies from 20 to 20,000 Hz
Below 20 Hz is infrasonic
Above 20,000Hz is ultrasonic

4. Speed of sound in various objects: Higher density objects tend to have a higher speed of sound.

5. Parts of a sound Wave: Wave front: area of compression
Wave length: distance from one compression to the next
Ray: Arrow indicating the direction of wave

6. Doppler Effect:
Q: Does the speed of a sound wave depend on the pitch or frequency? Q: What will happens to the distance between the waves in front of the source as it moves forward? How about behind? Results: Check the following web site

7. Doppler effect continue…
Waves in front of source become closer because waves cannot get away.
Waves in back of source get longer.
Shock waves are produced when source is traveling faster than speed of sound

15. Resonance: Natural frequency: Frequency an object vibrates at.
Swing/desk/ jar/ guitar/
Demo: Music
Demo: Spring
Demo: Tacoma bridge
Demo: Electric guitar and wine glass
How to break a tree
Designing cars
Designing engines

16. Resonance happens when:______________________________________________________________________________________________

17. Standing wave in pipes open at both ends:
Node: Regions of high and low compression that form within a pipe. Anti-node: Regions where the pressure remain unchanged. Fundamental frequency: natural frequency of pipe. Longer pipes have lower frequencies.

18. Fn = n v / (4L)
Fn: fundamental frequency or frequency of pipe (hz) n: number of nodes L: length of pipe v: speed of sound wave (343 m/s for air)

19. Problem: Find the frequency given off by a 2
Problem: Find the frequency given off by a 2.03 meter pipe, for nodes 1 through 3.
Frequency
Nodes
Frequency

20. Light: Has alternating electric and magnetic fields and travels at 3x108 m/s.

21. Electromagnetic Spectrum: Range of all of the frequencies of light.

22. Visible Spectrum: Range of visible frequencies of light

23. More properties of waves:
Refraction: The bending of light as it passes from one medium to the other

24. Diffraction: The bending of a wave around an object.

26. Polarization: When all of the directions of the light waves are aligned.