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:
   • Funniest Summer Wipeouts! Beach and S...  
For much more fails, visit their channel:    / @failarmy