Microscope


Everyone has heard of a microscope. We all used them in grade school to look at our cheek cells and then later in high school to look at a dissected frog or starfish. But how many of us actually remember the basics? Well here is a short refresher.

A microscope is...

Something to help you see small things. A microscope gathers light from a tiny area of a thin and well-lit specimen. It uses an objective lens that is small and spherical and brings the image under it into focus at a short distance. The image is then magnified by another lens called the eyepiece so that you can see it in more detail.

When you are looking through a microscope there are three things that determine the quality of your image:

Brightness – how light or dark is the image? This is related to the illumination system and can be altered by changing the voltage of the bulb under it. It is also related to the numerical aperture of the objective lens.

Focus – is the image blurry or well defined? Focus is related to the focal length and can be controlled by the focal knobs. The thickness of the cover piece also effects your focus—so the thinner the better.

Resolution – how close can two points in the image be before they are no longer two separate points? The higher the resolution the better you can see things in detail.

Parts of a Microscope

All microscopes, whether simple or complex, have these main components:
  • Stage – where the specimen rests
  • Clips – to hold the specimen in place
  • Lamp – produces the light so that you can see the specimen and sits underneath the stage
  • Objective lens – gathers light from the specimen
  • Eyepiece – magnifies the image
  • Tube – holds the eyepiece at the proper distance and blocks out stray light
  • Coarse focus knob – used to bring the object into overall focus
  • Fine focus knob – used to make fine adjustments to the focus
  • Arm – curved portion and also what you carry it by
  • Base – supports the weight
Some Notable Folks

Zacharias Janssen was the original inventor of the microscope in 1595. The first microscope consisted of a tube with lenses at each end. These lenses magnified specimens from 3X to 9X their size depending on the size of the diaphragm openings.

Robert Hooke improved the early compound microscope around 1660. He also coined the term ‘cell' to describe features of plant tissue.

Anton van Leeuwenhoek is better known for his work on the microscope. He made the simple microscope with only one lens. The microscopes he built were the best of his time and he was the first person to describe bacteria, protozoans and also helped prove the theory of blood circulation.

Microscopes can be simple or complex in design and some can do more than one type of microscopy but each reveals different information. The microscope has greatly advanced our knowledge about biology and science and will continue to be a powerful tool for scientists.

By Lisa Sharp           


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