a microscope that uses visible light & different lenses to produce an image of a specimen at upto x1500 bigger
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Magnification?
the size increase from the specimen to the image viewed in microscope
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Resolution?
'Maximum resolving power'- the distance between 2 objects before they look like one object
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Max resolution of light microscope?
200nm
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Specimen?
what you're viewing using microscope
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Staining?
Coloured stains allow specimens/features to be seen
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Sectioning?
A method of slicing specimens thinly without distortion- useful for analysing tissues e.g.brain
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Electron Microscope?
a microscope with high magnification and resolution, using electron beams instead of light & uses electron lenses, to make images of specimen
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Scanning Electron Microscopy?
electron beam is directed AT the sample,reflected of specimen into detector-makes a built up computerised 3D image.
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Transmission Electron Microscopy?
electron beam passes THROUGH a thinly prepared sample.Electrons can't easily pass thru denser parts-get contrast; then electrons pass onto a layer of film & a 2D image is made
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How does Staining help create images of specimen in Transmission EM?
Samples are stained to create contrast; some parts take up more stain than others= image created cos some parts will absorb more electrons than others
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What substances are typically used in dyes?
Heavy Metals e.g. Phosphotungstic Acid
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Magnification of Scanning EM?
upto x100,000
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Magnification of Transmission EM?
upto x500,000
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Advantages of Light Microscopy
relatively good magnification (upto x1500), good resolution (200nm), good enought to look at cells in education, research & labatory analysis, large range of samples can be viewed
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Disadvantage of Light Microscope
Resolution not high enough to see detail about the internal working of the cell e.g. internal structure of mitochondria
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Why do EM have a higher magnification and resolution than light microscopes?
resolution on light microscopes is 200nm,anything smaller merges-however, the wavelength of a beam of electrons is 0.004nm & is much smaller than wavelength of light, so can be absorbed by smaller organelles
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Scanning vs Transmission
scanning has higher magnification & resolution for 3D shapes-more realistic . Transmission: more detail
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Disadvantages of EM
1)electron beams can be deflated by air-so all EM must be done in a vacuum 2)Expensive 3)highly specialised pieces of equipment-can't be used by all 4)specimen must be killed,dehydrated & fixed with heavy metal stains before use 3)black & white image
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Laser Scanning Confocal Microscopy (LSCM) ?
modern method that uses laser light to show the different structures in cells without the need to slice the specimen thinly & with less blur
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How does LSCM work?
Specimen stained with fluorescent dyes that reflect laser light, the laser can be focused at many diff depths of the specimen-so u can build up a 3D picture of the cells scanned
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Advantages of LSCM
As the laser is focused at a specific depth, the out of focus light is not seen-so images clearler 2)Images can be taken at diff depths-so u can build up a 3D image of the cells scanned
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What is the equation for image size?
Image Size = Real Size x Total Magnification
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Total Magnification Equation?
Total Magnification = 10(eyepiece lens magnification) x Objective lens Magnification
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Graticule
ruler used to measure cells-consists of 2 components: Stage Micrometer/Slide Graticule + Eyepeice Graticule
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Differential Staining
Diff tissues will absorb diff dyes & so more than 1 dye can be used to show the diff types of tissue
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How to prepare a permanent slide?
1) fixed using formaldehyde 2)Dehydrated with ethanol 3)Set in Paraffin Wax 4)Sample can be sliced using a microtome & paraffin removed
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Other cards in this set
Card 2
Front
Magnification?
Back
the size increase from the specimen to the image viewed in microscope
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