Lecture23 - PHYSICS 231 INTRODUCTORY PHYSICS I Lecture 23...

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Unformatted text preview: PHYSICS 231 INTRODUCTORY PHYSICS I Lecture 23 • Speed of sound in fluid (for solid, replace ) • Intensity • Intensity Level - dB • Spherical Waves Last Lecture -Sound v = Β ρ β = 10 log 10 I I o I = I 10 b /10 I = Π 4πρ 2 B Y I = P A I =10- 12 W/m 2 Doppler Effect, Moving Observer Fig 14.8, p. 435 Slide 12 Towards source: Away from source: H ' = ω + ω ο ω ' = ω- ω ο ω Fig 14.9, p. 436 Slide 13 O Doppler Effect: Source in Motion λ ' = l- v s T = l- v s l v = l 1- v s v ( ) f ' = v l ' f ' = φ ω ω- ω σ λ λ Doppler Effect, Source in Motion Approaching source: Source leaving: f ' = φ ω ω- ω σ f ' = φ ω ω + ω σ Example 14.6 An train has a brass band playing a song on a flatcar. As the train approaches the station at 21.4 m/s, a person on the platform hears a trumpet play a note at 3520 Hz. a) 3300 Hz b) 9.74 cm c) 3106 Hz Fig 14.11, p. 439 Slide 15 Shock Waves (Sonic Booms) When the source velocity exceeds the speed of sound, Application: speed radar Application: weather radar Both humidity (reflected intensity) and speed of clouds (doppler effect) are measured. Doppler Effect: Both Observer and Source Moving Switch appropriate signs if observer or source moves away H ' = ω ω ο ω ω σ Example 14.7 At rest, a car’s horn sounds the note A (440 Hz). The horn is sounded At rest, a car’s horn sounds the note A (440 Hz)....
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Lecture23 - PHYSICS 231 INTRODUCTORY PHYSICS I Lecture 23...

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