History of the Microscope

A. Introduction 1. A microscope is an optical instrument that uses a lens or a combination of lenses to magnify and resolve the fine details of an object.

B. History of the Microscope 1. During the 1st century AD (year 100), glass had been invented and the Romans were looking through the glass and testing it. 2. They experimented with different shapes of clear glass and one of their samples was thick in the middle and thin on the edges. 3. They discovered that if you held one of these “lenses” over an object, the object would look larger.

4. Someone also discovered that you can focus the rays of the sun with one of these special “glasses” and start a fire. 5. These early lenses were called magnifiers or burning glasses. 6.The word lens by the way, is derived from the latin word lentil, as they were named because they resembled the shape of a lentil bean. 7. These lenses were not used much until the end of the 13th century when spectacle makers were producing lenses to be worn as glasses.

8.The early simple “microscopes” which were really only magnifying glasses had one power, usually about 6X - 10X. 9. One thing that was very common and interesting to look at was fleas and other tiny insects. These early magnifiers were hence called “flea glasses”.

10.Sometime about the year 1590, two Dutch spectacle makers, Zaccharias Janssen and his father Hans started experimenting with these lenses. 11. They put several lenses in a tube and made a very important discovery. The object near the end of the tube appeared to be greatly enlarged, much larger than any simple magnifying glass could achieve by itself! 12. They had just invented the compound microscope (which is a microscope that uses two or more lenses).

13.Galileo heard of their experiments and started experimenting on his own. 14. He described the principles of lenses and light rays and improved both the microscope and telescope. 15. He added a focusing device to his microscope and of course went on to explore the heavens with his telescopes.

16.Anthony Leeuwenhoek of Holland became very interested in lenses while working with magnifying glasses in a dry goods store. He used the magnifying glass to count threads in woven cloth. 17. He became so interested that he learned how to make lenses. 18. By grinding and polishing, he was able to make small lenses with great curvatures. These rounder lenses produced greater magnification, and his microscopes were able to magnify up to 270X!

19. Anthony Leeuwenhoek became more involved in science and with his new improved microscope was able to see things that no man had ever seen before. 20. He saw bacteria, yeast, blood cells and many tiny animals swimming about in a drop of water. From his great contributions, many discoveries and research papers, Anthony Leeuwenhoek ( ) has since been called the "Father of Microscopy".

21. Robert Hooke, an Englishman (who is sometimes called the “English Father of Microscopy”), also spent much of his life working with microscopes and improved their design and capabilities.

C. The Compound Microscope 1. In the basic compound microscope, the object to be magnified is placed under the lower lens (objective lens) and the magnified image is viewed through the upper lens (eyepiece lens). 2. The magnification of the image can be calculated by multiplying the magnifying power of the objective lens times the magnifying power of the eyepiece lens. 3. The microscope is composed of a mechanical system which supports the microscope, and an optical system which illuminates the object under investigation and passes light through a series of lens to form an image of the specimen.

The principle of the compound microscope. The passage of light through two lenses forms the virtual image of the object seen by the eye.

Eyepiece Objective Lens Magnificati on Low Power10 x 100 x Green = GO! High Power10 x43 x430 x Yellow = Caution Oil Lens10 x97 x970 x Red = STOP! Never Use This Lens! or 100 xor 1000 x

1.Don’t even think of starting your drawing unless you have a PENCIL! Drawings in PEN are UNACCEPTABLE! This is for two reasons: (a) You can erase pencil! (b) You can shade in areas more easily in pencil. 2. Each Drawing must be 1/2 page in size, and must include clear, proper labels! In the upper left hand corner of each circle include the specimen name as written on the slide label. In the upper right hand corner, include the magnification (100x or 430x).

2. Place ONE drop of water directly over the specimen. If you put too much water over the specimen, then the coverslip will float on top of the water, making it harder to draw the specimens as they float past the field of view! 3. Place the coverslip at a 45 degree angle (approximately), with one edge touching the water drop, and let go. How To Make A Wet Mount : 1.Gather a thin slice/piece of whatever your specimen is. If your specimen is too thick, then the coverslip will wobble on top of the sample like a see-saw: