moving one side of the breakwater gap system in the ripple tank, 

 results were achieved (figs. 29, 30) which bear out the theoreti- 

 cal computations. 



Resume and conclusions 



Several relatively simple problems in refraction and dif- 

 fraction have been covered by this paper. The reason for the 

 relative simplicity of these problems is the very nature of 

 the ripple tank itself, which has already been discussed. 



The formulation of the method of solution of problems in 

 refraction of ocean waves by complex bottom topography has been 

 presented by Eckart (1951) » but actual formal solutions have not 

 yet been found. 



Also of great interest is the theoretical work which has 

 been done in wave motion involving superposition of periods 

 (Pierson, 1951). Since the ripple tank is now only capable of 

 producing waves of one discrete period, it has been necessary 

 to forego discussion of these problems. 



However small the scope of this paper, it has been shown 

 that problems in the refraction and diffraction of light waves 

 and sound waves are analogous to problems in the refraction 

 and diffraction of water waves. The analogy has provided a means 

 for testing theoretical results and a way to observe waves in 

 motion. 



A more exhaustive search of the literature would undoubtedly 

 yield many more solutions to problems in wave propagation. A 

 catalogue of these problems would make a useful reference for 



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