4 ms·
I use a salt shaker and pour salt onto a plate - if I can make out single falling grain of salt on the way to the plate, I know this light source is not healthy
by xiconfjs 8y ago
I use a salt shaker and pour salt onto a plate - if I can make out single falling grain of salt on the way to the plate, I know this light source is not healthy for humans.
- jfengel 8y agoHang on, how does that work?