Microscopes

November 24, 2012 10:03 am

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Microscopes
How is it possible for something right in front of your eyes to be completely invisible? It’s possible when that thing is too small to be seen with your eyes.
We can see drops of water from a pond or lake. But we cannot see the thousands of tiny creatures that live in the water. Drops of blood contain tiny structures called cells, but we can’t see them either. Microscopes allow us to see invisibly small things.
Microscopes are one of the most important tools of scientists. Medical scientists use them to see the germs that make people sick. Biologists use them to see how plants and animals are constructed. Geologists—scientists who study the Earth—use them to find out what rocks are made of. Some microscopes are so powerful that they enable us to see individual atoms, the tiny building blocks of everything.
DIFFERENT KINDS OF MICROSCOPES
Some microscopes make tiny objects look larger using lenses that bend light rays. Microscopes that use light to look at small objects are called optical microscopes. The simplest optical microscope is a magnifying glass. The best magnifying glasses can make things look 10 to 20 times larger than they actually are.
The optical microscopes used by scientists are called compound microscopes. They contain several lenses. The scientist looks through a lens called the eyepiece to see the magnified object. Compound microscopes often have three different settings. Each setting provides a different magnification.
Optical microscopes can produce magnifications of up to about 1,000 times. To view even tinier things, scientists use microscopes called electron microscopes and scanning probe microscopes.
An electron microscope shoots tiny particles called electrons at the thing being viewed. Instruments turn the pattern of scattered electrons into an image on a screen. The best electron microscopes can produce images with magnifications up to 1 million times.
A scanning probe microscope uses an extremely tiny probe, or tip, to “feel” the surfaces of tiny objects. The end of the probe might have a width of just one atom. A scanning probe microscope can make images of the individual atoms on the surface of an object. Some scanning probe microscopes can magnify objects by as much as 100 million times.
WHEN WERE MICROSCOPES INVENTED?
Historians think the compound optical microscope was invented by a Dutch eyeglass maker, Zacharias Janssen, in the late 1500s. Most microscopes were not very good until the early 1800s. That is when lens makers first learned how to make lenses that produce really clear, sharp images. German scientists developed the first electron microscope in the early 1930s. The first scanning probe microscope was created by Swiss and German scientists in 1981.
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