I got 62% on the first 1/3 and then 78 % on the 2nd 1/3 for the periodic waves and motion chapter. I found watching chad's video on this topic before reading the text was helpful. Also I made sure I learned from my mistakes and that is why I jumped to 78% the second time through. Don't get too discouraged if you do poorly on a chapter, its how you learn from your mistakes that matters. However, if you are still scoring poorly on this content after reviewing your mistakes then perhaps seek other sources to help your understanding, i.e TPR book for this chapter or online resources like khan academy or chads videos. For example, i found TBR to be crappy for the electrostatics and magnetism chapter so I used TPR for that and I heard optics is even worse so I will probably end up using TPR for that chapter as well.
