I built a 1B FPS video camera to watch light move

Brian Haidet (Alpha Phoenix) shows how he made a video of a laser beam travelling across his garage. From his description:

I'm using the technique from the electricity waves video where I used repeated oscilloscope measurements synced after the fact to produce "videos" of electricity moving down a wire. The only difference is that instead of measuring electricity waves, I'm measuring light emitted by a laser, bouncing off the wall, traveling to my camera, and landing in the window of a photomultiplier tube.

what's gonna happen if we watch the double slit experiment using it?