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Micro Lesson 3 new Studentnotes

Micro Lesson 3 new Studentnotes - Lesson 3 Microscopy...

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Lesson 3 Microscopy: techniques used to study microorganisms The microscope: is the essential tool of the microbiologist. Because of the inability of the unaided human eye to perceive objects smaller than 0.1mm, a microscope is essential to see microbial cells and to determine their morphological (outline and shape) characteristics. used to see objects smaller than 0.1 mm based widely on Leeuwenhoek’s design 10x ocular 10x, 45x, 95x or 100x objective Leeuwenhoek’s microscope The earliest microscope based on Leeuwenhoek’s design was extremely simple. It consisted of a single piece of ground glass fixed between two perforated metal plates and it could magnify objects about 400 times. The compound microscope Today’s compound microscope employs a _______-lens system for magnification. Light enters in and passes through the specimen and is magnified through a series of lens The eyepiece is called the __________ and usually has a power of 10X, which means it magnifies the object 10 times, and the other lens through which the object is viewed is called the objective. The objective can be several different powers but it usually cannot be any higher than 100X. A typical compound light microscope will have a 10X ocular and _____ _______________ ______________which can be rotated into position, a 10X low power objective, one a 45X high power objective, and a 95X or 100X oil immersion lens. To calculate the total magnifying power of the microscope, multiply the ocular power by the objective power. For example, if the 10X objective is in place for viewing, multiply the 10X ocular by the 10X objective and you get 100X magnification power. In order to view bacteria at high magnification, the light must be concentrated and made stronger or the image will appear too dark, so the 95X or 100X oil immersion lenses must be used. A small drop of immersion oil, usually cedar oil, is placed on the slide over the bacterial smear and the objective is slowly lowered into the oil and focus. The oil helps to _____________ the light passing through it so that the image can be viewed. Newer compound microscopes have a_________ in the oil immersion objective to protect the slide. If the objective is lowered too far and actually touches the slide, 1
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the spring keeps the slide’s cover plate from fracturing. Older microscopes did not have this feature and the slide and the bacterial smears were at risk of damage if the user wasn’t careful. Compound microscopic parts: In addition to the optical parts, the compound microscope has several mechanical parts and an illuminating system. The mechanical parts include: 1. the body tube 2. a revolving nosepiece that houses the objectives 3. the stage 4. clips for the slides 5. coarse and fine adjustment knobs 6. an arm 7. a base. The coarse adjustment knob moves the body tube over a greater vertical distance, bringing the specimen into approximate focus.
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Micro Lesson 3 new Studentnotes - Lesson 3 Microscopy...

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