1. Mechanical Waves
Physical Science

2. 2. Mechanical Waves – vibrate matter
Transverse - matter moves perpendicular to direction the wave travels
Longitudinal (Compressional) - matter vibrates in same direction that wave travels

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

4. Transverse Wave

5. Longitudinal (compressional) Wave

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

10. 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.

11. 2 Types of Interference Reinforcement (Constructive) Interference
Crests and/or troughs of 2 waves add together, resulting in increased amplitude. Waves are in phase.

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

13. 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).