Passage
During deep underwater dives, scuba divers must overcome the external ambient pressure in order to expand their chests to inhale. To assist underwater breathing, air from scuba tanks is administered at high pressures to keep divers' lungs inflated. Scuba tanks are often filled with a mixture of N 2 and O 2 gas. Due to the increased pressure of the gases in the lungs, a greater amount of the gases are dissolved into the bloodstream during underwater dives. At a body temperature of 37°C, the solubility of N 2 gas in blood is 6.0 × 10 −3 mol/L⋅atm and the solubility of O 2 gas is 1.3 × 10 −2 mol/L⋅atm.If a diver ascends too quickly after an extended dive, there is an increased risk of vascular bubble formation. Due to the decrease in ambient pressure, the excess gas dissolved in the blood may come out of solution as gas bubbles and cause a number of adverse effects. This condition is known as decompression sickness, or "the bends." To avoid this problem, scuba divers limit their rate of ascension to allow the excess gas dissolved in their blood to be safely removed through respiration. Because gas bubbles are good reflectors of sound, these bubbles can be detected using Doppler ultrasonic flowmetry after the diver has surfaced.
Adapted from M. Spencer, Journal of Applied Physiology. ©1976 American Physiology Society.
-Which of the following wave characteristics would be observed to increase if the bubbles are flowing toward the Doppler ultrasonic flow meter?

Question

Passage
During deep underwater dives, scuba divers must overcome the external ambient pressure in order to expand their chests to inhale.  To assist underwater breathing, air from scuba tanks is administered at high pressures to keep divers' lungs inflated.  Scuba tanks are often filled with a mixture of N 2 and O 2 gas.  Due to the increased pressure of the gases in the lungs, a greater amount of the gases are dissolved into the bloodstream during underwater dives.  At a body temperature of 37°C, the solubility of N 2 gas in blood is 6.0 × 10 −3 mol/L⋅atm and the solubility of O 2 gas is 1.3 × 10 −2 mol/L⋅atm.If a diver ascends too quickly after an extended dive, there is an increased risk of vascular bubble formation.  Due to the decrease in ambient pressure, the excess gas dissolved in the blood may come out of solution as gas bubbles and cause a number of adverse effects.  This condition is known as decompression sickness, or "the bends."  To avoid this problem, scuba divers limit their rate of ascension to allow the excess gas dissolved in their blood to be safely removed through respiration.  Because gas bubbles are good reflectors of sound, these bubbles can be detected using Doppler ultrasonic flowmetry after the diver has surfaced.
Adapted from M. Spencer, Journal of Applied Physiology. ©1976 American Physiology Society.
-Which of the following wave characteristics would be observed to increase if the bubbles are flowing toward the Doppler ultrasonic flow meter?

Quizplus · Accepted Answer

11ecba2d_12c0_7549_a3bf_4f50d94bbeb9_MD0008_00 A flow meter is a device that measures the rate of flow, and ultrasound refers to high frequency sound waves. According to the passage, Doppler ultrasonic flow meters can be used to measure vascular bubble formation because gas bubbles are good reflectors of sound waves. When the bubbles are moving relative to the device, the observed wavelength and frequency differ from those of the original ultrasound signal (Doppler effect). The wavelength of a wave is the distance from one wave maximum to the next, and the frequency of a wave is the number of wavelengths that pass through a point per unit time. By definition, wavelength and frequency are inversely related to each other. When bubbles flow toward the device, each successive sound wave is reflected at a location closer to the device, decreasing its wavelength (Choice D). Therefore, the observed frequency would increase compared to the original frequency. (Choice B) The amplitude of a wave is related to its energy. The amplitude of a reflected wave decreases because a portion of its energy is transmitted into the bubble. (Choice C) The velocity of a wave depends on the medium in which it is traveling. Because the reflected wave travels in the same media as the original wave, their velocities are the same. Educational objective: When relative motion exists between a wave source and an observer, the frequency and wavelength of the observed wave differ from those of the original wave. Frequency increases and wavelength decreases if the sound source is moving toward the observer.

Passage During Deep Underwater Dives, Scuba Divers Must Overcome the External