over the one in which earlier refraction studies, for the Beach 

 Erosion Board, were made (Pierson, 1950). 



The tank is made of dxirable plexi-glass and is mounted about 

 three feet from the floor in a sturdy iron framework. Its di- 

 mensions are: 4 feet long, 3 feet wide, 3 inches deep. Figure 1 

 shows a photograph of the ripple tank. 



An improved audio-oscillator has been installed which is 

 capable of generating frequencies from one-half cycles per second 

 up to 8,000 cycles per second, and which controls a speaker magnet 

 that causes a long cylindrical rod to vibrate at one end of the 

 tank, producing parallel waves. It has been found that for the 

 most part, a frequency of eight cycles per second is most effective 

 in producing the desired results. 



In order to simulate wave motion in the ripple tank, we must 

 make some adjustments in the medium of propagation. The velocity 

 of a periodic wave of small but finite amplitude is given by 



where A = wave length 



g = gravitational force 

 c = wave velocity 

 ^ = surface tension 

 p = density 

 h = depth 

 Suppose a liquid to have no surface tension; then 



^ ^= (2.2) 



