2.1 Microscopy Flashcards
What does a microscope do
Produces a magnified image of a sample
Name the 4 types of microscope
Light microscope
Scanning electron microscope
Transmission electron microscope
Laser scanning confocal microscope
How does an SEM work
Scan a beam of electrons across specimen which knocks electrons of specimen which are collected in a cathode ray tube to form an image
Image type, max res, max mag, sample type of a SEM
3D
0.002 micro metres
< x500,000
Thin or thick
How does a TEM work
Uses electromagnets to focus beam of electrons which is transmitted through specimen. Fender parts absorb more electrons so look darker on the image
Image type, max res, max mag, sample type of a TEM
2D
0.0002 micro metres
> x1,000,000
Thin
How does a laser scanning confocal microscope work
Use laser beams to scan specimen which has been tagged with fluorescent dye. Laser causes dye to fluoresce. Light is focused through a pinhole onto a detector connected to a computer which generates an image. Image is 3D. Samples can be thick or thin
Type of microscope to use when presented with a photomicrograph
Light microscope
How to prepare a wet mount microscope slide
1) Place a droplet of water on slide
2) Place specimen on droplet
3) Carefully place cover slip on, avoiding air bubbles
4) Place drop of stain on one side of the cover
5) Place paper towel on other side to draw stain through sample
Why do slide preparations need to be thin
So the light can get through the specimen
How to use a stage micrometer to work out the distance represented by the small divisions of an eyepiece graticule
1) See how many eyepiece divisions make one stage division
2) Each stage division is 0.1mm so divide 0.1 by the amount of eyepiece divisions to fine the size of one eyepiece division
Why is staining useful for light microscopy
Staining allows you to distinguish between different parts of the sample as different parts absorb more/less dye so appear as different colours
Magnification formula
Magnification = image size/object size
What is resolution
Resolution is the clarity of the image - the ability of the microscope to distinguish between two points that are close together
What is magnification
How much bigger than the sample the image created is
