The video discusses the principles of optical interferometry using glass interfaces and a ZYGO GPI LC interferometer from the 1990s.
0:00 intro
2:13 What can you do with interferometry?
3:06 Optical wave fronts explained
12:41 Inside the ZYGO GPI LC interferometer
20:45 Example of visual fringe evaluation
The clip featuring a wave at 3:12 min was taken from this FailArmy video:
https://www.youtube.com/watch?v=r-V_r0UTs0g
For much more fails, visit their channel: https://www.youtube.com/@failarmy