The Compound Light Microscope s1

The Compound Light Microscope

Partners:

Biology Period D

Mr. LaRocca

October 20, 2014 Introduction:

The compound light microscope is one of the most popular types of microscopes known.

“Compound” stands for the multiple parts and objectives/lenses used to create the microscope.

“Light” stands for the light that is used to be able to see the specimen (The Compound Light

Microscope, n.d.). The microscope has many parts to it, all essential to see the specimen with an optimal view. It is a very delicate device and should be handled with extreme care. The compound light microscope allows the viewer to view extremely tiny objects with a unique accuracy and perception. Without the compound light microscope, many of the early scientific discoveries would not have been made.

Zacharias Jansen, born in the 1500s, is believed to be the creator of the first compound microscope. It is believed by historians that in 1590, with the help of his father Hans, Janssen was able to construct one of the most unique and important instruments in science. Janssen and his father Hans were both glass/spectacle makers in the late 16th century. They used this craft to their advantage by making the lenses and ocular out of glass for a crystal view of the selected slides. Historians believe that the first microscope Zacharias and Hans Janssen created was about two and a half feet long. It was made out of brass tubing and the eyepiece was about 2 inches in diameter (Zacharias Janssen, n.d.).

Anton van Leeuwenhoek was another scientist who made major contributions to the compound light microscope. Leeuwenhoek was sometimes referred to as the creator of the microscope which was a false statement because Janssen is believed to be the original inventor.

Despite this inaccurate statement, it is believed that Leeuwenhoek constructed over 500 microscopes in his life. These microscopes were very simple compared to those of Janssen. His microscopes had only one lens unlike those of Janssen and were only about three to four inches high. Janssen’s equipment was about two and a half feet high. Despite these differences in the microscopes, Leeuwenhoek’s microscopes were a lot better than Janssen’s. Leeuwenhoek’s microscopes could magnify objects to over 200x. Janssen’s best could only go up to 30x. This increase in magnification allowed Leeuwenhoek to formulate one of the first discoveries in bacteria. He studied the plaque buildup on people’s teeth and came to the conclusion that there were “animals” living inside of him (Leeuwenhoek, n.d.).

Robert Hooke was another influential scientist that worked with the compound light microscope. Hooke’s greatest discovery of the plant cells would not have been made without the use of the compound light microscope. With the use of his own microscope that he created, he was also able to see a multitude of different items. Hooke studied fossils, feathers, and even insects. Hooke used Leeuwenhoek’s microscope but criticized it because he believed that it was a strain on the eyes. Because of this, Hooke built his own microscope that he used for his own discoveries (Hooke, n.d.).

The purpose of this lab is to learn how to use the compound light microscope. By learning how to use the compound light microscope, new objects can be studied and used in future lab assignments. The hypothesis for this lab is if the object is placed under a microscope, then the image shown will be reversed and flipped.

Methods + Materials: The first part of this lab was to adjust the compound light microscope to create an optimal view for the specimens. After this was done, a prepared slide, an “e,” a clean slide, a pipette, and a coverslip were brought to the lab bench. A wet mount was created by putting the “e” on the clean slide. Using the pipette, a drop of water was placed on the “e” and the slide. A coverslip was used to seal the wet mount. Then either the prepared slide or the wet mount was placed under the microscope. The results were recorded in the lab manual. Then the other slide was viewed and that data was also recorded.

Results:

A compound light microscope has many parts to it. The eyepiece, also known as the ocular, is where the specimen is viewed. It leads into the body tube and the nose piece, which holds the high and low power objectives. The high and low power objectives increase the magnification of the specimen. Obviously the high power objective will increase the magnification more than the low power objective but the difference in magnification depends on the type of microscope used. The objective lenses can move in and out based on the adjustment knobs. There are two knobs, one known as the coarse adjustment knob, and the other known as the fine adjustment knob. These knobs help increase or decrease to fine tune the view of the slide. The stage and the stage clip holds the slide in place for the viewer. The diaphragm controls the amount of light used from the light source. The arm, base, and inclination joint all keep the microscope together.

The microscopes used in the biology lab have specific magnifications for the objectives and the eyepieces. Table 1 refers to the magnifications of the eyepiece, objectives, and even the total magnification. The magnification of the eyepiece remains the same at 10x with each objective. The low power objective begins at 4x while the medium power begins at 10x. The high power starts at 40x. To find the total magnification, the magnifications of the objectives were multiplied by the magnifications of the eyepieces.

Figures 1 and 2 show the view of the thread and the “e” used in the wet mount. In figure

1, the thread is shown under a magnification of 40x. Then the thread is shown under the medium power where the field of view is decreased. Figure 2 showed what happened to the “e” when under the microscope. In the low power, the “e” is fully visible. When in the medium power, part of the “e” is not visible because the increase in magnification decreases the field of view.

Discussion:

The compound light microscope is a great tool to have and it should be in every lab. This lab explained how the compound light microscope should be used and how to use it effectively.

The lab explained that the microscope was a delicate device and that it should be treated with extreme care. In order to do this, one hand should be placed under the base while the other hand should be on the arm of the microscope. This lab also taught that the image of an object is flipped and reversed when viewed through the ocular. As shown through the lab, the high and low power objectives increase and decrease the field of view. It also taught that the coarse adjustment knob should not be used with the high power objective under most circumstances. References

Antony van leeuwenhoek (1632-1723). (n.d.). Retrieved October 19, 2014, from Berkeley.edu

website: http://www.ucmp.berkeley.edu/history/leeuwenhoek.html

The compound light microscope. (n.d.). Retrieved October 19, 2014, from Miamioh.edu website:

http://www.cas.miamioh.edu/mbiws/microscopes/compoundscope.html

Robert hooke. (n.d.). Retrieved October 19, 2014, from Berkeley.edu website:

http://www.ucmp.berkeley.edu/history/hooke.html

Zacharias janssen. (n.d.). Retrieved October 19, 2014, from Fsu.edu website:

http://micro.magnet.fsu.edu/optics/timeline/people/janssen.html