1. Reflection A wave is reflected when it comes into contact with a barrier A wave is reflected when it comes into contact with a barrier Law of Reflection – The angle of incidence is equal to the angle of reflection Law of Reflection – The angle of incidence is equal to the angle of reflection θ i = θ r

2. Reflection (cont’d) Angles are with respect to the normal (perpendicular line drawn to the surface) Angles are with respect to the normal (perpendicular line drawn to the surface)

3. PHYSICS OF SOUND

4. Sound Sound is a series of atmospheric pressure waves produced by a vibration Sound is a series of atmospheric pressure waves produced by a vibration Longitudinal wave Longitudinal wave MUST have a medium to travel through MUST have a medium to travel through

5. Sound Waves Amplitude – Loudness Amplitude – Loudness Frequency – Pitch (high or low) Frequency – Pitch (high or low) Humans have a hearing range of 20 Hz to 20000 Hz Humans have a hearing range of 20 Hz to 20000 Hz

6. Intensity of sound is measured in decibels (dB) Intensity of sound is measured in decibels (dB)

7. Resonance When one object vibrating at the same natural frequency of a second object. When one object vibrating at the same natural frequency of a second object. This forces that second object into vibrational motion. This forces that second object into vibrational motion. DEMOS – Tuning Fork and Water Tube DEMOS – Tuning Fork and Water Tube Video – Tacoma Bridge, Breaking Glass Video – Tacoma Bridge, Breaking Glass

8. Speed of Sound Speed of Sound in air at STP is 3.31x10 2 m/s + 0. 6T (T = Temperature in Celsius) Speed of Sound in air at STP is 3.31x10 2 m/s + 0. 6T (T = Temperature in Celsius) Speed of Sound depends on the Temperature. Speed of Sound depends on the Temperature.

9. Doppler Effect The change in frequency of a wave due to the motion of the source or of the receiver.

10. Doppler Effect Small λ Higher f Large λ Lower f

11. Shock Waves Video

12. Challenge Problem Wayne shouts down a well and hears the echo of his voice.85 seconds later. How deep is the well? (Note: At STP) Wayne shouts down a well and hears the echo of his voice.85 seconds later. How deep is the well? (Note: At STP)