8-58. What will happen to light rays which 

 enter water at an angle of 90°? 



1. They will bend toward the normal 



2. They will slow down but remain 

 parallel 



3. They will bend away from the normal 



4. They will speed up but remain 

 parallel 



8-59. When a beam of white light is passed 

 through a prism, the colors of the 

 spectrum are visible due to 



1. reflection 



2. refraction 



3. diffusion 



4. diffraction 



8-60. A mirage is an optical illusion caused 

 by which of the following? 



1. Light reflection 



2. Light diffraction 



3. Light refraction 



4. Light diffusion 



8-61. Which of the following mirages would 



cause a distant image to appear inverted 

 in the sky? 



1. Superior 



2. Lateral 



3. Inferior 



4. Vertical 



8-62. Beams of light which are especially visi- 

 ble in a hazy or humid atmosphere and 

 appear to diverge from the sun both just 

 before and just after sunrise and sunset 

 are called 



1. halos 



2. rainbows 



3. iridescent rays 



4. crepuscular rays 



8-64. The frequency of sound is measured in 



1. hertz 



2. meters per second 



3. vibrations per second 



4. feet per second 



8-65. Which of the following must be present 

 before sound can be produced? 



1. A source of sound only 



2. A detector to hear the sound only 



3. A medium to transmit the sound only 



4. A source, a detector, and a trans- 

 mitter of sound 



8-66. The particles of a medium through which 

 a longitudinal sound wave is passing 

 will react in what manner? 



1. They will move at right angles to 

 the wave's direction of travel 



2. They will move in all directions 

 independent of the wave's direction 



3. They will move back and forth along 

 the wave's direction of travel 



4. They will remain stationary 



8-67. The speed at which sound will pass 



through a given substance is basically 

 dependent upon what characteristics of 

 the substance? 



1. Density and temperature 



2. Elasticity and density 



3. Elasticity and temperature 



4. Density and conductivity 



8-68. In addition to density, which of the 

 following factors affect the velocity 

 of sound through sea water? 



1. Pressure only 



2. Current 



3. Temperature only 



4. Pressure and temperature 



8-63. The interference of light rays from the 

 sun or moon by clouds which are small in 

 comparison to the wavelength of the light 

 rays produces a phenomena called 



1. rainbows 



2. cloud halos 



3. cloud iridescence 



4. crepuscular rays 



8-69. The pitch of a sound wave is governed 

 by which of the following sound wave 

 characteristics? 



1. Frequency 



2. Intensity 



3. Speed 



4. Wavelength 



Learning Objective: Relative to the 

 properties of sound, describe how 

 its frequency is measured, elements 

 necessary before sound can be pro- 

 duced, characteristics of sound 

 waves, factors that influence sound 

 velocity in a substance, capabili- 

 ties of the human ear as a detector, 

 and the application of sound in 

 SONAR operation. 



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