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54 Cards in this Set
- Front
- Back
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What are the primary metric units used to measure microbes?
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Micrometer and Nanometer
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Meter symbol?
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m
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Decimeter symbol?
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dm (1/10 of a meter)
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Centimeter Symbol?
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cm(1/100 of a meter)
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Millimeter Symbol?
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mm(1/1000 of a meter)
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Micrometer Symbol?
And use? |
um(1/1000 of a mm)
Use to measure cells |
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Nanometer Symbol?
And use? |
nm(1/1000 of a um)
Use to measure organelles and viruses |
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Definition of Microscopy?
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Use of light or electrons to magnify objects
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The Microscopy principles
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wavelength of radiation
contrast of the specimen resolving power of the scope magnification of an image |
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What is red's nm?
What is violet's? |
650 red
400 violet |
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Which side of the color spectrum is longer?
Which is shorter? |
Longer->ROYGBIV<-Shorter
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Do smaller or longer wavelengths enhance Microscopy?
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Shorter
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Modern microscopes use what kind of wavelengths? (include color)
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Short
Blue light or electron beams |
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What is magnification?
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The apparent increase in size of an object
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When does magnification occur?
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When radiation refracts (alters/bends) as it passes through a lens
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Why do curved glass lenses work?
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They bend light because they are optically dense as compared to the air.
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As light enters a lens what does it do?
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It slows down and bends.
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When does a lens refract light rays the most?
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When it passes through the periphery as compared to the center
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Where does the lens focus light rays?
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The focal point
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What do light rays do as they pass through the focal point?
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The light rays spread apart to form an enlarged image
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What effects the degree to which an image is enlarged?
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The lens thickness,
lens curvature, and the speed of light as it passes through the substance |
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What does the clarity of a magnified object depend on?
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Resolution and contrast
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Definition of resolution.
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Resolution is the ability to distinguish between objects that are close together
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What is the resolution of a modern microscope?
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0.2 um
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What does resolution distance depend on?
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wavelength of the electromagnetic rays
and numerical aperture of the lens |
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Definition of aperture.
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Aperture refers to the ability to gather light.
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What is the Resolution distance formula?
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0.61 x wavelength
resolution distance = --------------------------- numerical aperture |
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Definition of contrast.
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Differences in intensity between 2 objects, or between object and background
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When does light increase contrast?
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When all the light waves' crests and troughs are aligned.
Called phase. |
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What is a bright-field?
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When the background/field is illuminated
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What is a dark-field?
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The background is dark, therefore, the specimen appears light
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Definition of phase.
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uses of alignment of light waves to achieve contrast between specimen and background
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Definition of fluorescent.
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uses ultraviolet light to cause specimens to radiate visible light or fluorescence
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Definition of confocal.
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uses lasers to illuminate fluorescent chemicals in a thin plane of a specimen
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What is a simple bright-field microscope like?
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A magnifying glass
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How do you calculate the magnification in a compound microscope?
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in series (ocular + objective)
10x ocular X 4x scanning = 40x magnification |
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What are the compound objectives called?
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scanning lens 4x
low-power lens 10x high/dry lens 40x oil immersion lens 100x |
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What does the oil immersion lens increase?
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magnification
and resolution |
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The oil between the slide and objective allows the lens to do what?
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Increases the ability to capture light, does not refract, oil increases the numerical aperture
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Why are the objective lenses important?
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They bend light rays
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How is total magnification of a compound microscope calculated?
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By multiplying the magnification of the objective lens by the magnification of the ocular lens.
Ex. 10x ocular lens X 100x oil immersion objective = 1000x magnification |
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What is the limit of useful magnification for light microscopes?
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2000x
resolution is restricted by wavelength of visible light |
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What is phase used for?
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Examining living specimens that would be altered by staining or attachment to a slide.
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What's differential interference contrast?
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use prisms to split light and create more contrast
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What's the range of wavelengths in electrons?
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0.01nm and 0.001nm
HIGHER RESOLVING POWER |
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When resolving power is high so is....
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magnification
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With electron microscopy, what is the range of magnification?
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10,000x to 100,000x
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Electron microscopes are good to use when you need to see what?
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Details of viruses, bacteria, organelles, molecules, and large atoms
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What are the two types of electron microscopes?
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Transmission electron
and Scanning electron |
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What does an SEM microscope use?
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Magnetic fields within a vacuum tube to manipulate a beam of electrons.
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What can be seen with a SEM?
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whole specimens, sectioning not required
ONLY DEAD ORGANISMS only magnifies external surface |
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How does a TEM work?
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Generates a beam of electrons that produces an image on a fluorescent screen
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What must the column be?
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It must be a vacuum and the specimen must be very thin
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With a TEM you can see what?
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Only DEAD ORGANISMS
must be dehydrated and sectioned |
