You should be able to find copies of in class notes and necessary handouts in the folders below.
This video talks about "refraction" of ocean waves but gives a good visual display of what we are calling "diffraction" in ocean waves. Key spot is between 1st and 2nd minute of the video.
Watch especially around the 4.5 minute mark where he shows waves being generated in a pond as it is a great visual of what we need to know.
A GREAT explanation of concepts we have learned even if it is a bit deeper than the level we have learned. Not all of what is shown in the ripple tank is easily visible on the video. Some great real world examples.