1.1 cell structure - magnification and microscopically

define magnification

the number of times bigger an image appears compared to the size of the real object

define resolution

the smallest distance between two objects that can be distinguished

how does a light microscope work?

passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed

what are the advantages of a light microscope?

• inexpensive

• easy to use

• portable

• observe both dead and living specimens

what is the disadvantage of light microscopes?

limited resolution

how does an electron microscope work?

if uses a beam of electrons which are focused using magnets. the electrons hit a fluorescent screen which emits visible light, producing an image

name two types of electron microscope

• transmission electron microscope (TEM)

• scanning electron microscope (SEM)

what is the advantage of electron microscopes?

greater magnification and resolution

why do electron microscopes have a greater magnification and resolution?

they use a beam of electrons which has a shorter wavelength than photons of light

how have electron microscopes enabled scientists to develop their understanding of cells?

• allow small sub cellular structures (eg mitochondria and ribosomes) to be observed in greater detail

• enable scientists to develop more accurate explanations about how cell structure relates to function

what are the disadvantages of electron microscopes?

• expensive

• large so less portable

• require training to use

• only dead specimens can be observed

how can the magnification of an image be calculated

magnification = size of image/size of real object