1. Take out your Mechanical Waves notes packet
Do Now – Answer on your Do Now Sheet Silently and Independently (Really)
A fire truck has it’s siren blaring. It drives towards you and then passes you. What happens to the sound AS IT DRIVES PAST?
Take out your Mechanical Waves notes packet

2. Which Way Did That Thing Go?
Sound & Doppler Effect

3. Bell in a Jar.

4. Sound Waves in Gas, Water, Liquid

5. Sound Facts Sound is transmitted as a LONGITUDINAL wave.
Sound is a mechanical wave so it requires A MEDIUM TO BE TRANSMITTED.
Speed of sound in…
air: 331 m/s
sea water: 1435 m/s
steel: 5100 m/s
Amplitude of a sound wave is synonymous with VOLUME, LOUDNESS, INTENSITY

6. Changing Sound?

7. Phenomenon #5 – Doppler Effect
A source sends out waves in all directions with the same frequency and wavelength.
How the wave is perceived by an observer depends on RELATIVE MOTION of the source and/or observer.

8. Phenomenon #5 – Doppler Effect
Same frame of reference (no relative motion)
FREQ. OBSERVED (FOBS) = SOURCE FREQ.(FSOURCE) A B

9. Phenomenon #5 – Doppler Effect
Getting closer together – FOBS > FSOURCE
… at increasing speed – GETTING HIGHER
… at decreasing speed – GETTING LOWER
Getting farther apart – FOBS < FSOURCE
… at increasing speed – GETTING LOWER
… at decreasing speed – GETTING HIGER B A

10. Doppler Constant Speed Doppler Changing Speed

11. Mini-Whiteboards
What differences did you hear in the constant speed v.s. increasing speed Doppler Effect?

12. End of PRACTICE