Laser Microscope

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Light, Cells and Microscopes, Microbiology

Alternative titles: Viewing Microbes with a Laser and Water Droplet

Summary

A laser is focused through a water droplet at the tip of a syringe, which acts as a convex lens. The light is projected onto a screen, allowing small aquatic organisms and impurities in the water to be observed.

Procedure

Fill a syringe with pond water or another sample containing microorganisms.
Place the syringe on a stand so that a droplet of water forms at the needle tip.
Set up a white screen about 1 meter away.
Position a laser (a laser point is sufficient) about 2 feet away from the droplet.
Align the laser beam so it passes through the water droplet, projecting an enlarged spot on the screen.
Gently adjust the syringe piston to maintain a stable droplet size.
Darken the room and observe small moving shapes within the light, which show microbes and particles in the water.

Links

Laser Microscope Made With a Drop of Water - The Action Lab:

Laser Microscope - The Sci Guys:

📄 Laser Microscope Experiment - element 14: https://community.element14.com/challenges-projects/project14/provingscience/b/blog/posts/laser-microscope-experiment

Variations

Use different light sources (red, green or blue lasers) to test visibility of microbes.
Prepare a hay infusion by soaking hay in water for several days to cultivate microorganisms for observation.
Compare results with filtered water to demonstrate water purity.

Safety Precautions

Never look directly into the laser beam or point it at eyes.
Handle syringes with care; avoid accidental pricks from the needle.
Perform the experiment on a stable surface to prevent spills.
Wash hands after handling pond water or other biological samples.
Keep laser devices out of reach of young children.

Questions to Consider

Why does the water droplet act like a convex lens?
How does the laser light interact with microorganisms to make them visible?
Would a microscope using visible white light show clearer details than the laser method? Why?
How might the wavelength (color) of the laser affect what you see?
What are some limitations of this laser microscope compared to standard optical microscopes?