micrb202 exam1

micrb202 exam1 - MICRB 202 Exam 1 Notes Experiment 1 The...

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MICRB 202 Exam 1 Notes Experiment 1: The Compound Microscope Compound microscope – multiple lenses in sequence Bright-field, phase-contrast, fluorescence – types of light microscopes Electron microscopes – use electron beams instead of light, include transmission EM (TEM) and scanning EM (SEM) Resolving power – the ability of a lens system to distinguish two points that are very close together as two separate points. A function of numerical aperture, the wavelength of light being used, and the condensor. Sometimes blue light is used to increase resolution (blue light is the shortest-wavelength visible light) Numerical aperture (NA) – a term that measures the light-gathering ability of the lens Condensor – controls how light is delivered to specimen Diaphragm – varies the amount and shape of the cone of light that enters the specimen. Closing down diaphragm and using less light can increase contrast. Oculars (eyepieces) – lenses where the eyes are placed, 10x mag Nosepiece holds the four objective lenses scanning lens (4x), low dry lens (10x), high dry lens (40x), oil immersion lens (100x) Immersion oil – refractive index equal to that of glass, used to fill the space between the glass slide and glass objective lens Working distance – space between the objective and specimen when the lens is in focus, smaller with higher power lens Depth of field – thickness of a “slice” of specimen that will be in focus with a particular lens. More shallow at higher magnifications. Carry scope by base and arm , adjust coarse focus first, use mechanical stage control to move slide around under the objective, use fine focus for fine-tuning, diopter adjustment ring to adjust each individual eyepiece The maximum useful magnification of a light microscope is 1200x (our scopes go up to 1000x) Parfocal – once the microscope is focused using one objective, switching to another objective should not greatly affect the focus Resolution – the ability to see objects that are close together as multiple distinct and separate objects Numerical aperature – term describing the light-gathering ability of a lens (higher NA more light gathered greater resolution) In order to make meaningful observations, bacteria must be viewed under 100x oil immersion lens. The magnifying power of a scope = (power of objective lens) x (power of ocular lens) Experiment 3: Aseptic Technique Microorganisms are ubiquitous – found virtually everywhere Mixed culture – contains multiple species Pure culture – only one kind of organism is growing in any one culture vessel Contamination of a culture – introduction of other species Sepsis – life forms Aseptic technique – designed to prevent contamination of a culture Sterile – free of any living thing Growth medium – must be suitable for the particular organism being studied, can be liquid broth
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This note was uploaded on 04/17/2008 for the course MICRB 202 taught by Professor Keating during the Spring '08 term at Penn State.

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micrb202 exam1 - MICRB 202 Exam 1 Notes Experiment 1 The...

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