I noticed the same thing when I was playing the guitar. The constant flickering combined with a vibrating string at a high frequency produces a nice looking eff

I noticed the same thing when I was playing the guitar. The constant flickering combined with a vibrating string at a high frequency produces a nice looking effect [1], which can be observed with a naked eye (unlike the one in the video). [1] https://www.youtube.com/watch?v=ttgLyWFINJI https://www.youtube.com/watch?v=ttgLyWFINJI