electron microscope

Question 1

what are the two main advantages of electron microscope

Answer 1

the have an electron magnet so the electrons can be focused as they are negatively charged onto the magnet
they also have a shorter wwavelength which results in higher resoling power so objects closer together can be seen as seperate objects

Question 2

why does a vacuum need to be used what does this mean

Answer 2

in order to avoid air molecules colliding with the beams of the electron thus only non living species can be observed

Question 3

what is transmission electron microscope

Answer 3

electron are fired at a thin piece of specimen some of the specimen absorb the electrons and appear dark and the parts whci hallw eletrons through appear white this then produces a photomicrograph

Question 4

what are the limitation of transmission electron microscope

Answer 4

the specimen needs to be extremly thin so its easily damaged by high energy electron
there is no colour due to complex staining process
vacuum so lining things cannot beobserved
artefacts can be producedwhcih appear on the final photomicrograph which have been produced whilst preparing specimen

Question 5

what is scanning electron microscope

Answer 5

electons beamed are reflected and scanned on the specimen in a regur order the scattered electrons are collected and the scattering is dependent on the contour of the specimen we can then build up a 3d picture of the specimen

Question 6

how to work out length of an object

Answer 6

calibrate an eyepiece graticule with a stage micrometer to find out how much one unit is on a stage micrometer

Question 7

why cant you slide the cover slip

Answer 7

to prevent cells rolling over each other to ensure cell is one layer thick

Question 8

how to prepare a sample for a light microscope

Answer 8

place a drop of water on the slide place one cell layer thick sample on the slide add stain use mounted needle to place coverslip on top