Problem 5. (Use your indoor voice) A person shouting at the top of his lungs emits about 1.0 mW of energy as sound waves. What is the sound intensity level at: A. 1.0 m from such a person? Use units of dB. B. 5.0 m from such a person? Use units of dB. C. How far from the person would the sound intensity level be 10 dB less than the sound intensity level at 5.0 m? Problem 4. (An underwater source) An underwater source of sound produces spherical waves in a freshwater lake. The intensity of the sound 5.0 m from the source is 7 X 10'3 W/mz. A. What is the intensity 2.0 m from the source? Use units of W/mz. B. What is the total power of the source? Use units of W. C. Would either of your answers to parts A or B above change if the lake had saltwater in it instead of freshwater? 3. Both the answers to A and B would change. b Only the answer to A would change. c. Only the answer to B would change. d Neither the answers to A nor B would change. Problem 1. (Wave forms in space and time) The graphs below describe a wave propagating along a string. The left-hand graph shows the vertical displacement of the string as a function of time, at a fixed x-coordinate on the string; the right-hand graph shows the shape of the string at a fixed time. 3: (nun) A. What is the frequency of the wave in units of Hertz? B. What is the wavelength ofthe wave in units of meters? C. What is the speed of the wave in units of m/s? Problem 3. (Sound waves in different mediums) Substance Density p (kg/m3) Speed 1/ (m/s) Dry Air (STP) 1.217 340 Fresh Water (20 \"C) 9.982 x 102 1.41 x 103 Seawater (20 C) 10.25 x 102 1.54 x 103 A sound wave travels in the +x-direction through a straight pipe filled with seawater (20 C). The frequency of the wave is 1000 Hz. Suppose that at t = 0.0 s and at x = 0.0 m the gauge pressure is a maximum. A. At t = 0.0 5, what is the location (in In) ofthe next maximum pressure in the +x direction? Suppose, instead, the sound traveled through dry air, which of the following quantities would change? a. Speed b. Wavelength c. Frequency At t = 0.0 5, what is the location (in m) ofthe first maximum away from the origin for sound traveling through dry air in the +xdirection? D. Fill in the blanks in the equation below that describes the vertical displacement y of this wave as a function ofx and t. Pick the correct values from the list below which fill in the blanks from left to right. J'vat) = (___mm) 05[21T((___ m'1)x (__S'1)t)] 2.5,2.5, 0.5 0.2,5.0, 0.5 4, 0.2, 0.5 4, 5, 2.5 4, .0.2, 2.5 SPF-99'!\" E. In what direction is the wave described by the equation above moving? a. Positive x-direction b. Negative x-direction Problem 2. (Travelling wave) A wave traveling to the right is shown as a function of position here at two different times: t = 0.000 s and then 0.010 5 later. A. What is the speed of the wave assuming the wave has not traveled more than one wavelength (in units of m/s)? B. What is the wavelength (in cm)? C. What is the frequency of the wave (in Hz)