Whats 1000 nanometres equivalent too in micrometers?
1um
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Whats the definition of resolution?
The minimum size of an object that can be seen.
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Whats the resolution of the light microscope?
0.0002mm (This means that 2 points this distance apart are viewed as separate objects)
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What's the wavelength of visible light/ light microscope?
Between 400 - 700nm
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What happens to the rays when objects are about half the size of the wavelength of visible light?
The rays of light are interrupted and are resolved in the light microscope.
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Why cant objects smaller than 0.0002mm be seen?
They are too small to interrupt the light.
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What's the definition of magnification?
The ratio between the actual size of an object and an image of that object.
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What triangle helps you to calculate the magnifications or actual sizes of objects?
The I A M triangle (Magnification = size of image / actual size)
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Whats the wavelength of an electron beam/ electron microscope
1 nm (so objects half this size are visible)
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What's the useful magnifications of an electron microscope (SEM & TEM)
SEM - up to x100 000. TEM - up to x250 000.
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How does an electron microscope work?
magnets focus beams of electrons and an image is formed when the electrons strike to florescent screen or photographic film.
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What are the two types of electron microscope?
Transmission electron microscope & scanning electron microscope.
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Whats the TEM used to view?
Thin sections of tissues
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Whats the SEM used to view?
surfaces of 3D objects e.g. bodies of insects & surfaces of cells.
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Why is there a vacuum inside electron microscopes?
It allows electron to travel towards the specimen and afterwards strike a florescent screen or a photographic film.
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Give an advantage of using the light microscope rather than the electron microscope.
In a light microscope its possible to watch living processes, such as cell division.
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Give a disadvantage of using an electron microscope.
Living cells cant be observed since they would explode.
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What's the useful magnification of the light microscope?
up to x1000 (at best x1500)
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What's the resolution of the light microscope?
200nm
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What's the resolution of the electron microscope?
0.5nm
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Why do biological materials need to be stained?
Because most biological material is colourless/transparent & is composed of elements with a low atomic mass - so visible light travels through tissues in the LM without being absorbed or reflected so theres very little contrast if any.
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Give three examples of stains used to stain biological material.
Iodine, methylene blue and toluidine blue.
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Stains used in electron microscopy are _____ of _____ _______ such as uranium and lead. These combine with ______ e.g. cell membranes and absorb or _______ e - as they pass through the specimen. Makes these areas show _____ on photo taken using EM.
Salts, Heavy, metals, proteins, scatter, dark.
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Other cards in this set
Card 2
Front
What is 1000 micrometers equivalent too in umm?
Back
1umm
Card 3
Front
Whats 1 nanometre equivalent too in micrometers?
Back
Card 4
Front
Whats 1000 nanometres equivalent too in micrometers?
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