Figtire l6. 



Figure 17. 



Figure I8. 

 Figure 19. 



Figure 20. 

 Figure 21. 

 Figure 22. 



Figure 23. 



Figure 24. 



Figure 25. 

 Figure 26. 

 Figure 27. 



Figure 28. 



Figtire 29. 

 Figure 30, 



List of Illustrations (Cont.) 



Page 



Photograph showing total reflection of 



water waves at the boundary of the step 



model 39 



Photograph showing an infinite screen 



(Jetty) placed at the zone of transition 



between deep and shallow water 40 



Diffraction of plane monochromatic light 



by a black half -plane 43 



Photographs showing diffraction by a rigid 

 breakwater. Angles of incidence are 

 approximately ^^^ and 40" 45 



Diffraction by an infinite slit (sound) ... 48 



Diffraction by an infinite slit 49 



Photograph showing diffraction by a 

 breakwater. The width of the gap is small 

 compared with the wave length ^2 



Photograph showing diffraction by a 

 breakwater. The width of the gap is large 

 compared with the wave length 53 



Photograph showing diffraction by a 



breakwater. The width of the gap is very 



large compared with the wave length 54- 



Arrangement of source, straight edges and 



plane of observation 55 



Curve of light intensity for coplanar 



straight edges, d = 0; 6 = 0.4b cm 57 



Experimental curve of light intensity (solid 

 line) with corresponding theoretical curve 

 (broken line) for d = 40 cm. and 6 = 0.44 cm. 57 



Experimental curve of light intensity (solid 

 line) with corresponding theoretical curve 

 (broken line) for d = 80 cm. and 5 = 0.56 cm. 57 



Photograph showing increase in dissymmetry 



of the diffraction pattern as d is increased. 58 



Photograph showing increase in dissymmetry 

 of the diffraction pattern as d is increased 

 still further 59 



viii 



