Assignment 12 



Fundamental Oceanography; Administration; Publications; Supply; Security 



Text: Pages 380 - A20 



Learning Objective: Relate temp- 

 erature gradient, pressure, and 

 ocean bottom topography with 

 sound propagation in the ocean 

 environment, to include identi- 

 fying reaction of sound rays 

 under given conditions and spec- 

 ified transmissions. 



12-1. Refer to figure 16-5 in your textbook. A 

 negative vertical temperature gradient 

 causes sound rays to 



1. bend up toward the horizontal 



2. bend up toward the vertical 



3. bend down toward the horizontal 



4. bend down toward the vertical 



In items 12-2 through 12-4, select from column B 

 the temperature gradient identified by each 

 definition in column A. 



A. Definitions 



12-2. Temperature gradient 

 along a plane at 

 boundaries between 

 water masses or cur- 

 rents 



12-3. Temperature decrease 

 with depth 



12-4. Temperature change 



within a given water 

 mass from the sur- 

 face downward 



B. Gradients 



1. Vertical 



2. Horizontal 



3. Positive 



4. Negative 



12-5. Which type of temperature gradient causes 

 a shadow zone? 



1. Positive vertical 



2. Positive horizontal 



3. Negative vertical 



4. Negative horizontal 



12-6. The longest sonar ranges are possible 

 under which of the following basic 

 patterns? 



1. Negative temperature gradient 



2. Isothermal temperature pattern only 



3. Isovelocity structure only 



4. Isovelocity structure and isothermal 

 temperature pattern 



12-7. Which of the following combinations of 

 sea conditions and sound propagation 

 patterns is correct? 



1. Negative temperature gradient, posi- 

 tive velocity structure, downward 

 refraction 



2. Positive temperature gradient, posi- 

 tive velocity structure, upward 

 refraction 



3. Negative temperature gradient, 

 isovelocity structure, downward 

 refraction 



4. Positive temperature gradient, nega- 

 tive velocity structure, upward 

 refraction 



12-8. Interference of sound beam transmission 

 in shallow water is a result of 



1. the depth of the sea in the area only 



2. the characteristics of the sea sur- 

 face and bottom only 



3. the speed of sound in the sea area 

 only 



4. the depth of the sea in the area, 

 characteristics of the sea surface 

 and bottom, and speed of sound in 

 the sea area 



12-9. If a sonar pulse with a wavelength of 

 500 feet is sounded in water where the 

 depth is 80 fathoms, which of the fol- 

 lowing statements is a valid assumption? 



1. The bottom surface consists of sedi- 

 ment 



2. The bottom surface consists of sand 

 and rock 



3. Sound is likely to be propagated in 

 the bottom surface 



4. Sound is not likely to be propagated 

 in the bottom surface 



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