A simple laser pointer can help you see the tiny bugs that crawl around in liquid all the time. Will this make you appreciate the simple ways to see the richness of life? Or will you bleach everything you come in contact with? Try it and see!
A laser doesn't have to be powerful to do impressive things. A simple laser, like the ones used to torment your cat, can be your gateway to the microscopic world. All you need is a few drops of filthy water, a way to suspend the drops, and the ability to shut the cat out of the room so it doesn't mess up the experiment.
The water has to be in droplet form - as in the drops that you see hanging from icicles when they melt or the tips of your fingers when you take a shower. A syringe held by a stand would be a good way to get a dangling drop, but it's possible to also use a regular needle or pin, a piece of string, or a pencil. Just let the water run down it until it's hanging as a droplet from the end of the instrument.
The water can't be clean either. You'll have to visit a pond or grab some from a puddle in a field. (If you do have a cat, you can probably get some good stuff from the cat bowl when you go to change it after a day or two.) Shine the laser through the rounded end of the drop, and stare at the projection of the light on the wall behind the drop. You should be able to see the shadows of little things moving around in there.
The laser light will hit the curved wall of the drop and get bent inwards to focus, the way the lenses of glasses focus incoming light. After the focus point, the light fans out again. When projected against a wall, that fanned light shows blurry pictures of the critters inside the droplet. The creatures either block the parts of the light or distort the light waves dramatically. These distorted light waves interfere with the incoming light, and so there are areas of extreme light and extreme shadow, which shows us the contours of the microscopic organism.
Check out a video of it below:
Top Image: Laser Pointer Forums
Via The Naked Scientists.