HW15-solutions

HW15-solutions - kuehner (rjk679) – HW15 – Mackie –...

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Unformatted text preview: kuehner (rjk679) – HW15 – Mackie – (20211) 1 This print-out should have 7 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Sound level β in decibels is defined as β ≡ 10 log parenleftbigg I I parenrightbigg , where I = 1 × 10 − 12 W / m 2 . The decibel scale intensity for busy traffic is 80 dB. Two people having a loud conversation have a deci- bel intensity of 70 dB. What is the approximate combined sound intensity? Correct answer: 0 . 00011 W / m 2 . Explanation: Let : β 1 = 80 dB , β 2 = 70 dB , and I = 1 × 10 − 12 W / m 2 . I = I 10 β/ 10 , so the combined sound intensity I is I = I 1 + I 2 = I parenleftBig 10 β 1 / 10 + 10 β 2 / 10 parenrightBig = (1 × 10 − 12 W / m 2 ) ( 10 8 + 10 7 ) = . 00011 W / m 2 . 002 (part 1 of 2) 10.0 points Two sound sources radiating in phase at a fre- quency of 560 Hz interfere such that maxima are heard at angles of 0 ◦ and 20 ◦ from a line perpendicular to that joining the two sources. The velocity of sound is 340 m/s. y L d S 1 S 2 θ listening direction θ δ Assume: L ≫ d Find the separation between the two sources. Correct answer: 1 . 77517 m. Explanation: Let : f = 560 Hz , v = 340 m / s , θ 1 = 0 ◦ , and θ 2 = 20 ◦ ....
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This note was uploaded on 03/24/2010 for the course PHYSICS 2202 taught by Professor Mihalisin during the Spring '09 term at Temple.

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HW15-solutions - kuehner (rjk679) – HW15 – Mackie –...

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