Microscopy
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Name the three types of microscope-
• Light • Scanning electron (SEM) 3.transmission electron (TEM)
Name the three types of microscope-
• Light • Scanning electron (SEM) 3.transmission electron (TEM)
How does an light microscope work?
-light focused using glass lense -relies on light passing through specimen -region that absorbs more light appear darker
Advantages and disadvantages of an light microscope?
A- easy to use, cheap (<£1000),true colour, can use live specimen D- low resolution, low magnification, specimens are Thin- may not be representive
How does an electron microscope work?
-uses electrons -short wavelength- high resolution -specimens not directly abosrbed- computers form images based on how many electrons are absorbed in different areas -focused using electromagnets
How does an SEM form an image?
Creates image based on how many electrons refelcted
Advantages and disadvantages of SEM’s?
A- much higher resolution, provides detailed images, high magnification (100,000x) D- expensive, require training, sample must be dead
How does an TEM create an image?
Creates image based on electrons abosrbed
Advantages and disadvantages of TEM’s?
A-much higher resolution, detailed images, high magnification (500,000x) D- expensive, require training, sample must me dead
Equation for magnification?
Mag= image size/actual size
Magnification definition?
How much biggrt an image appears to be compared with original size
Resolution definition?
Minimal distance between two point where they can still be viewed as separate objects
Why are graticules used?
Too help measure the width of the cell
Why is a stage micrometer used?
Allows us the callibrate the eyepiece graticule to allow us to know how much each measurement of the graticule actually is
Describe the four main types of sample preparation?
Dry mount- thin slices or whole specimens is viewed with just cover slip Wet mount- when water is added to specimen before lowering cover with a mounted needle to prevent air bubbles Squash slides- wet mounts which are pushed down on to ensure a thin layer Smear slides- placing a drop of the sample at one end of the slide and smearing it across with another slide. A cover slip is placed on top.
What are the different stains?
-methylene blue (stain negatively charged materials) -Congo red (stains background and make cells stand out)