Importance of the microscope The invention of the microscope has opened up a whole new dimension in science. By using microscopes scientists were able to discover the existence of microorganisms, study the structure of cells, and see the smallest parts of plants, animals, and fungi. Today, the microscope is still a commonly used tool to diagnosis illness in hospitals and clinics all over the world. Since their original invention, microscopes have moved beyond the simple visible light refracting lenses. Electrons, x-rays, and infrared rays are used by far more sophisticated (and expensive) microscopes to detect even smaller and smaller structures. Scanning electron microscopes are able to resolve viruses, which are far smaller than any cell.

Different types of Microscopes   Compound Dissection Scanning Electron Microscope (SEM) Transmission Electron Microscope (TEM) Description Compound microscopes are light illuminated. The image seen with this type of microscope is two dimensional. This microscope is the most commonly used. You can view individual cells, even living ones. It has high magnification. However, it has a low resolution. A dissection microscope is light illuminated. The image that appears is three dimensional. It is used for dissection to get a better look at the larger specimen. You cannot see individual cells because it has a low magnification. SEM use electron illumination. The image is seen in 3-D. It has high magnification and high resolution. The specimen is coated in gold and the electrons bounce off to give you and exterior view of the specimen. The pictures are in black and white. TEM is electron illuminated. This gives a 2-D view. Thin slices of specimen are obtained. The electron beams pass through this. It has high magnification and high resolution.

History Hans and Zacharias Janssen, Robert Hooke 1590, Dutch Eyeglass Makers, Inventors first compound microscopes (2 lenses), tube with lenses at each end Robert Hooke 1635-1703, English Chemist, Mathematician, Physicist, and Inventor Compound Microscope improvement Antonie van Leeuwenhoek 1632-1723, Wine Assayer, Surveyor, Cloth Merchant, Minor Public Official, and Inventor Simple Microscope (1 lens)

Types of Microscopes Simple- light passes through one lens (ex: magnifying glass) Compound – light passes through object first, then through 2 lenses Stereoscopic (Dissection) – similar to compound microscope but objects are 3D Scanning Electron – uses an electron beam, instead of light; gives a 3D image of the surface of the specimen Transmission Electron - uses an electron beam, instead of light; provides detailed image of the molecules inside the cell; 2D image

Total Magnification Objectives Low – RED – 4x Middle – YELLOW – 10x High – BLUE – 40x Total Magnification = Objective x Eyepiece _____ x 10 = Total Mag Magnification of Eyepiece = 10x

Microscope Always start on the lowest objective (red 4x) Move the coarse knob first to get the object in site, then move the fine adjustment to bring the specimen in focus. When asked to, move to the next highest objective (yellow 10x). Do not use the coarse adjustment, only the fine adjustment. When asked, repeat for the high objective (40x)

“e” Lab Concluding Questions State two procedures which should be used to properly handle a light microscope. Explain why the light microscope is also called a compound microscope. Images observed under the light microscope are reversed and inverted. Explain what this means. Explain why the specimen must be centered in the field of view on low power before going to high power. Describe the changes in the field of view and the amount of available light when going from low to high power using the compound microscope. Explain what the microscope user may have to do to combat the problems in question #5. How does the procedure for using the microscope differ under high power as opposed to low power?