Optical Microscopes

Many of us have used an optical microscope at home or in the classroom. Optical microscopes focus visible light through a combination of lenses to produce a magnified image of an object, say a flea's leg. Scientists used glass lenses and mirrors to focus and magnify light on an object. To increase the magnification of a microscope, more lenses are added to the instrument.

Optical microscopy can distinguish objects in the micrometer range, which is about 10-6 meters. However, the resolution power of these instruments is limited to revealing objects down to about 200 nanometers to 250 nanometers magnifications. The tiniest objects we could see would include red blood cells and small bacteria.

Optical microscopes have technical limitations too. A bacterium can be seen through a microscope that works with visible light because the bacterium is larger than the wavelength of visible light. However, tinier

^ Amazing Creatures with Nanoscale Features, the video is an introduction to microscopy and applications of nanoscale properties. http://www.cneu.psu.edu/edToolsActivities .html.

can see a video of one of these state-of objects such as atoms, molecules, and viruses are invisible because they are smaller than the wavelength of visible light. Therefore, they do not reflect the light of the image toward our eyes.

Although the optical microscope allows us to see many images, it leaves a lot of objects that we cannot see, such as viruses, atoms, molecules, and the DNA helix. To see these objects, we need other kinds of nonop-tical microscopes, called na-nomicroscopes.

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