microscope

the number of times larger an image is compared with real size of the object

the ability to distinguish between two separate points. if two points can’t be resolved, they will be seen as one point

all organisms are composed of one or more cells the cell is the basic organisational unit of life all cells arise from pre-exisiting cells

light transmission electron microscope scanning electron microscope

has 2 lenses [eyepiece and objective lens]

a beam of electrons with wavelength of less than 1nm is used to illuminate a vacuum inside the machine ensures the beam travels in a straight line

can see details of organelles much higher resolution than light microscope can magnify objects more than 500000x two main types - TEM,SEM

very large, must be operated in special rooms affected by magnetic fields preparation of material is lengthy, requires expertise and sometimes complex equipment all images are black and white expensive to purchase and operate beam can damage specimen complex specimen prep process can damage the specimen

fixation using chemicals or freezing staining with heavy metals dehydration with solvents TEM samples then set in resin and may be stained again SEM samples may be fractured to expose the inside and then coated with heavy metal

scan a beam of electrons across the specimen from above the electrons are scattered by the specimen according to the contours of the specimen surface a computer can then analyse the pattern of scattered electrons to build up a 3d image image show the surface of a specimen and can be 3d

transmission electron microscope

use electromagnets to focus a beam of electrons which is then transmitted through a thin section of specimen and focussed to produce an image denser parts of the specimen absorb more electrons which then makes them look darker on the image other parts allow the electrons to pass through and so appear bright can only be used on thin specimens

quick and simple to set up inexpensive

low resolution low magnification