From Looking Glass Universe.

This video is about the biggest lie people are told about the double slit experiment: that electrons are particles when they’re observed, but waves when they’re not. The truth is much more interesting.

Wave simulation website: https://www.falstad.com/ripple/
Paper about the single photon at a time version of the experiment: https://pubs.aip.org/aapt/ajp/article/84/9/671/1057864/Video-recording-true-single-photon-double-slit