Microscopy Flashcards
Magnification
The degree to which an image is bigger than the object (specimen) being viewed under a microscope.
Resolution
a measure of the microscope’s ability to distinguish between two points which are close together on an object.
Total magnification
magnifying power of eyepiece lens x magnifying power of selected objective lens
image/actual
Transmission Electron Microscope
Transmits a beam of electrons through specimen (stained with metal salts) to form an image
specimen usually has thickness of <100nm and is chemically dehydrated and stained
Magnification: up to x2 million (new gen up to 50 million) (>500,000)
Resolution: 0.2nm-0.002nm
Dead specimen -> viewed while in vaccum
electrons form 2D B+W image when photographed
small subcellular structures visible
Highest magnification and resolution, artifical colour
Scanning electron microscope
Electrons do not pass through specimen- secondary E- bounces off surface to focus on screen
Magnification: x15-x20,000 (up to 100,000- greater than light/ laser scan)
Resolution: Up to 10nm (greater than light, less than TEM)
B+W but computer programmes add false colour- 3D
specimen must be dead- in vaccum and coated with film of metal
high M+R, surface of sample visible only, artificial colour
Light Microscope
Uses visible light and a system of lenses to generate image
Magnification: x1500-2000
Resolution: limited
wavelength- 400-700nm
can view large cell structures
2D images- coloured by stain
can study whole living specimen eg. subcellular structures in plants
cheap, portable, used in school
Lowest magnification and resolution
Laser scanning microscope
Uses laser light to scan an object point by point and assemble pixel info on an image
Magnification: x17000
resolution: 800nm
2D/3D- Colour (stains can be used)
can clearly observe whole living specimens and cells in layers
Produces cross section images through specimen
used in medicine and bio research
M+R higher than light, lower than electron
Eyepiece Graticule
Measures the width of a cell
Stage micrometer
Quantifies graticule so we know how much each part of a specimen is worth
