The light microscope is the work of many centuries of science, first with the invention and use of lenses, and then with the perfection of lenses and illumination. Today, in many classrooms, students use a light microscope that can be powered by electricity with the use of a plug and outlet. This type of microscope is relatively inexpensive but gives incredible detail to very small objects placed on the base for viewing. Light microscope types include the compound and fluorescence light microscopes. Unfortunately, the light microscope by principle can never see anything smaller than half the wavelength of light.
The beginnings of light microscopy came about after the invention of glass lenses, an integral part of its design and function. In 1590, Zaccharias Janssen discovered lenses in a tube had compounding properties. In 1609, Galileo improved on the design. Anton van Leeuwenhoek's microscope was considered a simple microscope because of its single lens design, but his finely crafted lens allowed him magnifications of up to 270 diameters. Using these lenses he observed bacteria, plants, water drops and blood capillaries.
Light microscopy is the use of the light microscope as a research and observation tool. The light microscope is one of the most widely used and readily available devices for organic and inorganic research. Learning to use contrast, resolution and finding the focal plane are important to using a light microscope. Even an inexpensive light microscope can provide incredible views impossible to see with the naked eye.
Compound Light Microscope
The compound light microscope has more than one lens, making it compound instead of simple in design. Today's optimal compound microscope has a magnifying power of 1,000 to 2,000 times. A light microscope can give details of cell walls, bacteria, and even small details like cellular components and nuclei details.
Fluorescence Light Microscope
The fluorescence light microscope is a heavy-duty research grade microscopy equipment, not usually available to the general public. This microscope uses higher intensity light to excite fluorescence in the sample, which then emits light of a longer wavelength. The magnified images collected are due to the fluorescence of the sample and not the high intensity light used to stimulate it. This creates a much higher clarity not possible before.
A micrometer, or micron, is equivalent to one thousandth of a millimeter. Light microscopy uses white light which has a wavelength of about 0.55 microns. Light microscopy cannot observe details smaller than half of white light's wavelength, or about 0.275 microns. Details this small are either blurred or invisible. Because of this limitation, the electron microscope is used for details too small for a light microscope.