Friday, December 14, 2007

Robert Hooke and the Microscope

Robert Hooke on the Microscope.

Robert Hooke was a English physicist. In 1665 he looked at a silver of cork through a microscope lense and noticed some “pores” or “cells” in it.
In 1665, the English physicist Robert Hooke looked at a sliver of cork through a microscope lens and noticed some "pores" or "cells" in it. Robert Hooke believed the cells had served as containers for the "noble juices" or "fibrous threads" of the once-living cork tree. He thought these cells existed only in plants, since he and his scientific contemporaries had observed the structures only in plant material.
Robert Hooke wrote Micrographia, the first book describing observations made through a microscope. The drawing to the top left was created by Hooke. Hooke was the first person to use the word "cell" to identify microscopic structures when he was describing cork. Hooke also wrote Hooke's Law -- a law of elasticity for solid bodies.

-insert pic of microscope-


A telescope must gather large amounts of light from a dim, distant object; therefore, it needs a large objective lens to gather as much light as possible and bring it to a bright focus. Because the objective lens is large, it brings the image of the object to a focus at some distance away, which is why telescopes are much longer than microscopes. The eyepiece of the telescope then magnifies that image as it brings it to your eye.

1. Ocular lens or eyepiece: ours are 10x magnification. The scopes we will use are monocular (one eyepiece only.)
2. Body tube: contains mirrors and prisms which direct the image to the ocular lens.
3. Nosepiece: holds the objective lenses, rotates, note the positive stops for each lens.
4. Objective lenses: usually 3-4 on our scopes, 4x, 10x, 43x, 100x oil immersion (red banding). Total magnification = ocular power x objective power.
5. Stage: platform on which slides are mounted for viewing; some scopes have mechanical stages. Learn how to clip the slide in position properly.
6. Diaphragm: the diaphragm controls the amount of light which passes to the specimen and can drastically affect the focus of the image. LEARN TO USE THE DIAPHRAGM AS QUICKLY AS POSSIBLE. MOST PROBLEMS YOU WILL HAVE FOCUSING WILL BE DUE TO INCORRECT ADJUSTMENT OF LIGHT.
We have two types:
iris diaphragm: Look for a lever just under the stage near the front.
dial type: Just below the stage is a rotating dial having different size apertures (holes); this type is useful for creating a pseudo dark field effect.
7. Focusing knobs: Located on side of microscope; outermost is the fine focus and innermost is the coarse focus. 8. Light source: our scopes have built in light sources. The pushbutton switch is located (most often) behind the light lens on the base.