1. Mechanical Waves
Physical Science

2. Anatomy of a Wave #3 #2 #4 #1 #5 #6

3. 2. Mechanical Waves – vibrate matter
Transverse - matter moves perpendicular to direction the wave travels

4. 2. Mechanical Waves – vibrate matter
Longitudinal (Compressional) - matter vibrates in same direction that wave travels

5. Surface – combination of transverse & longitudinal, producing circular motion
Ex. Earthquake or Ocean waves

7. Velocity of Sound Sound must be transmitted through matter
Velocity depends on medium
v at 0o Celsius is 332 m/s, 344 m/s at 20o degrees C
Travels faster through warm air
Faster through solids & liquids

8. Loudness & Pitch Intensity of sound depends on amplitude
Loudness describes a person’s response to intensity
Measured in decibels - dB
Scale on next slide
Pitch - Way a person hears frequency (Hertz)

12. A hummingbird beats its wings up and down with a frequency of 80. 0 Hz
A hummingbird beats its wings up and down with a frequency of 80.0 Hz. What is the period of the hummingbird's flaps?

13. Radio station KSON in San Diego broadcasts at both 1240 kHz (AM) and 97.3 MHz (FM). a) How long is each? (kilo = 1000 & mega = 106)

15. Medium Frequency
Red - longest waves
Blue - shortest waves

16. Interference Produced when waves overlap.
Follows the Law of Superposition, which states that 2 waveforms combine in a manner which simply adds their respective amplitudes linearly at every point in time.

17. 2 Types of Interference Reinforcement (Constructive) Interference
Crests and/or troughs of 2 waves add together, resulting in increased amplitude. Waves are in phase.

18. 2. Cancellation (Destructive) Interference
Crest of 1 wave overlaps with trough of another, canceling each other out. Waves are out of phase.

19. Doppler Effect
When the source of the wave moves closer to you, the waves are compressed and the frequency (pitch for sound) goes up. The waves spread out as the source moves away, decreasing frequency (or pitch).