A point source is moving to the right with speed us. Figure 16.25 (a) A source Smov- ing with a speed v, toward a sta- tionary observer Aand away from a stationary observer B. Observer A hears an increased frequency, B and observer B hears a decreased frequency. (b) The Doppler effect in water, observed in a ripple tank. Letters shown in the photo refer to Quick Quiz 16.9. b Courtesyofthe Educational DevekpmentCenter, Newton, MA

Two sources are 7.2 cm apart and vibrate in phase at 7.0 Hz. A point on the third nodal line is 25.0 cm from one source and 27 cm from the other. (a) Calculate the wavelength of the waves. (b) Calculate the speed of the waves.

(a) To appreciate the human ear’s twelve order of magnitude (10^12) span from barely audible to the pain threshold, consider the following. Suppose an equivalently dynamic instrument were designed to measure distances. Taking the lower limit of the instrument to be 1.00 mm, what would be the largest distance measurable? (b) To provide a perspective for the human ear’s frequency sensitivity range (audible frequency extremes differ by 10^3 ), consider a speedometer with a similar speed range. If the speedometer’s maximum speed reading is 90.0 mi/h, what is the smallest finite speed that it could register?

For testing purposes, a musical instrument manufacturing company creates a device so that when you blow into one end with your instrument, sound comes out the other end in opposite directions. A sound technician uses a whistle and generates sound waves with a frequency of 200 Hz. The waves travel in opposite directions in a sound studio, are reflected by end walls, and return. The studio is 50.0 m long and the whistle is located 14.0 m from one end. What is the phase difference (in degrees) between the reflected waves when they meet at the source of the sound? The speed of sound in air is 343 m/s.