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Catherine Co Physics: Optical Instrument Paper March 7, 2019

Optical Instrument: Compound Optical Microscope Optics is a branch of physics which examines and explains the travel of light and its interactions with matter. Light waves can be bent and reflected to form new and altered images. Devices that process light waves to enhance an image for a clearer view are called optical instruments. These tools help one to see better by enlarging the object, therefore giving a more detailed image. Examples of optical instruments are magnifying lenses, telescopes, microscopes, and cameras. These instruments use mirrors and lenses to reflect and refract light to form images. Humans are in continuous contact with optical instruments and understanding the properties of lenses is essential to become familiar with the instruments. One optical instrument that will be discussed here is the compound optical microscope as it has performed a revolutionary function in biology and medicine. The optical microscope has led scientists to discover the secrets of the natural world that no other invention has. It has allowed scientists to find many discoveries including the discovery of cells, identification of bacteria, discovery of viruses and even the visibility of atoms. The optical microscope is the first and simplest type of microscope as opposed to the much more advanced electron microscope. The earliest simple microscope was a tube with a plate that had a lens on one end to magnify less than ten diameters, ten times the actual size of an object. Although it is impossible to say who invented the microscope, Dutch spectacle makers Hans Janssen and his son Zacharias Janssen are often said to have invented the first compound microscope in 1590. Galileo Galilei was also titled the inventor of the microscope as he developed the compound microscope with a convex and concave lens in 1609. In the late 17th

century, Antony Van Leeuwenhoek made the first real microscope. His simple microscope consisted of a single lens and was hand-held. The compound optical microscope uses a set of many lenses to maximize magnification. All optical microscopes consist of the same basic components: the eyepiece or ocular, objective lens, stage, and illumination source. For a compound microscope, a combination of the lenses can be used to get higher magnification as the first lens acts as the object for the second lens. A microscope has a magnification of up to 1000 using two lenses in combination. The objective lens is a converging lens with a relatively short focal length. The eyepiece is a magnifier that further enlarges the image created by the objective lens. The compound optical microscopes are usually used for examination of a smear, a squash preparation, or a thinly sectioned slice of material. It uses light passing through the sample from below and adjustment is required to illuminate the sample and increase the contrast. The diagram below is a representation of the principle of an optical compound microscope. The compound microscope uses refraction since it has several lenses that light passes through and bends to form an image by two stages. The first step is the objective lens as it forms the real inverted image. Second, the eyepiece further enlarges the real image, called the erect virtual image. In short, the last image observed is an inverted virtual image. Refer to AB in the diagram as a specimen and A’B’ as the primary image (magnified image) of the inverted real image created with the objective lens. The image is again magnified by the ocular lens or eyepiece. When higher magnification is required, the nose piece is rotated after low power focusing to bring the objective of a higher power in line with the illuminated part of the slide. When the eyepiece is arranged so that the primary image A’B’ is located closer to the eyepiece than the anterior focal point, the enlarged virtual image A”B” will be created. Looking from the eye (pupil) position on the eyepiece will allow one to see the enlarged image. In general, this

instrument creates a magnified image by combining an objective lens making an inverted real image and an eyepiece making an erect virtual image. The optical microscope has made an immense impact on the world and influence on the development of modern medical, forensics, and environmental science. The invention of the microscope has revolutionized the science industry and will continue to do so in the future. For example, the microscope helped doctors to spot abnormal cells and identify types of cells. This will help in identifying and treating new diseases as time goes on. The microscope will also help the ecosystem as it allows biologists to identify the types and number of organisms sustained in samples from ecosystems. It also has a great impact on the study of genetics. By allowing scientists to determine genetic abnormality, regeneration and tissue death, they will be able to find future cures and preventive medicines. The possibilities are endless with the use of the microscope as it will continue to create a better understanding in the field of science for humans in the future. microscope as it will continue to create a better understanding in the field of science for humans in the future.

Citations Ball, C. S. (n.d.). The Evolution of the Microscope. Retrieved March 12, 2019, from https://daily.jstor.org/the-evolution-of-the-microscope/ Knowledge Optical Microscopes. (n.d.). Retrieved March 12, 2019, from https://www.olympus-ims.com/en/microscope/terms/feature10/ Wolniak, S. M. (n.d.). Principles of Microscopy. Retrieved March 12, 2019, from https://www.life.umd.edu/cbmg/faculty/wolniak/wolniakmicro.html...