The Laser-drop-method: Making Microorganisms Visible Without a Microscope Using a Simple Laser Pointer

In order to get students and the general public excited about physics and biology, you need experiments that are as simple and exciting as possible. They should be interesting but also inexpensive to promote interest in scientific experimentation. A drop of water acts like a magnifying glass, allowing you to see particles trapped inside it. All you need is a usual red or green laser pointer and a plastic syringe. Simply draw the water to be examined into the syringe and squeeze out a drop that just hangs from the tip of the syringe. By simply shining a laser beam through a drop of water hanging from the tip of the syringe, the particles are cast as magnified shadows on any wall (screen). This ‘laser drop method’ can be used to examine, view and measure microorganisms and green algae from ponds, pools and lakes. Even oral mucosa cells from the mouth and hairs can be magnified and made visible using the ‘laser drop method’. In addition, all zooplankton can be observed in the water droplets as very agile and free-swimming organisms. This method is very simple and a low-cost science activity, and is suitable for outdoor excursions, in lecture halls for students and in the classroom of higher grades as well as for demonstrations to the general public, as a tool of applied physics and biology. Home experimentation is also possible with the ‘laser drop method’.