Microcopes: types Flashcards
What is an optical micorscope?
= uses light and lenses to form an image of the specimen
advantages:
= cheap and easy to use + study living cells
= coloured
=
disadvantages:
= low magnification and resolution- limited due to the wavelength of light
= 2d imagery
What is an electron, scanning microscope?
= uses electrons to form an image of the specimen
advantages:
= 3d imagery
= higher resolution and magnification
disadvantages:
= must be done in a vaccum
= expensive
= dead cell
= thin
= heavy staining
What can you see/not see in an optical microscope?
= small organelles are not visible
= living examples
= coloured
What is an transmission electron microscope?
= thin specimens, stained and placed in a vaccum
= electron gun produces a beam of electrons that passes through-specimen
= some parts absorb the electrons and appear dark
= 2d imagery- detailed images on interal strucyures
What is a scanning electron microscope?
= specimen does not need to be thin- electons are not transmitting through
= electrons beamed onto surface and scattered
= 3d imagery
How to calibrate an eye peice graticule?
= used to measure the size of objects
= each time changing the objective lens the magnificaton changes
= calibrate the eye peice
What is used to calibrate it?
= stage micrometger
= glass slide with a scale on it
= 2mm long
= intervals are 10 micrometers
How do we calibrate it?
1; line up stahge micrometer and eye peice gratoule whilst looking through eye peice
2: count how many divisions on the eye peice graticle scale fit into 1 division on micrometer scale
3; each division is 10 micrometers so this can be used to detemrmone the division on the eye peice is at the current magnification
What is the equation used?
I=Am
= image size = actual image x magnification
What are the units?
= metre (m)
= milimeter (mm)
= micrometre (um)
= nanometer (nm)
= converting downwards is x 1000 each time
= conveting upwats is /1000 each time
