Physics 1B Discussion Worksheet 5 Problem 1 For sound radiating uniformly from a point source show that the di erence in sound intensity levels 1 and 2 at two detectors is related to the ratio of the distances r1 and r2 from the source to the detectors by the expression 2 1 20 dB log10 r1 r2 1 Problem 2 If two adjacent harmonics of an organ pipe are 0 55 kHz and 0 65 kHz what are the length and fundamental frequency of the pipe Take v 340 m s Problem 3 Two speakers are driven by an identical oscillator at frequency 200 Hz The speakers are located 4 m apart on a vertical pole A person walks straight toward the lower speaker in the direction perpedicular to the pole starting from very far away Take the speed of sound to be 340 m s How many times will the person hear a minimum in the sound intensity and how far are they from the pole at these times o 1 10 B log Bz B 10 og f 1og 10 A lop B log Bn b 181g z 1010g f 2 20L Bz B 10g 0 25f 1 fn Fn 1 n 15 fofo 100 Hz L i N 2 100 7 200L 748 L 1 7m stopped TN Fn 2 100H2 2f0 fo 50Hz Fo 2 2 isol 3 dx 1r m 1 X vz n 1 m 12 X b x m fn n 1 p ap n E v d d 1 o L E n 1 E 2 d n 3 E d n 35 e 2Cn z Ed L d 22 n 1 E 2 24 1