In this clip the teacher leads a discussion tying the period bar applet to the unit circle.
Sine Period Bar Applet, Clip 3, 1:32
The teacher makes the move to ask the students how the inputs differ (or what they differ by) between two ends of the period bar. This will help reinforce what it means to have a period of 2Pi.
The student's question about the "next set of wavelengths" is a little unclear so the teacher probes to uncover her thinking. He then centers a discussion about period around her question. This will both answer her question and help other students better understand period.