Laser Projection Microscope
See the unseen!
A fun little 2 minute project to keep you awake at night
For best results use a fairly powerful laser pointer ~250 mW.
different water has different stuff in it.
this was a rather boring tap water sample. others aren't so boring...use your imagination
There are no obvious bacteria in that water sample. the dots you see are likely just dust and wood. bacteria will show up as longer more complex shapes like sausages or tetris pieces.
Depending on the strength of your laser this can be projected over several meters to really zoom in on what's in your water.
This works because of the collimated nature of laser light and the propensity of a water drop to form a sphere giving it a natural lens effect. The collimated light makes it focus free.