microscopes
how does a transmission electron microscope work?
*the beam of electrons pass through the specimin- which a stained with metal salts - they are controlled by condenser magnets *some electrons pass through the object and the objective and projector lens *and are then focused on the screen or photographic plate *the elctrons form a 2D black and white image (gray- scale)
resloution if a scanning electron microscope?
0.1nm
resolution of a transmission electron microscope
0.1nm
steps of useing a light microscope
1- specimin on a slide is placed on the stage 2- secured with the stage clips 3-while veiwing trough eye peice adjust the iris diaphragm for optimum light 4- ensure the object you are vewing is directly over the hole in the stage 5 roatate the nosepeice and bring the x10 objective into place over the specimin 6- look down the ocular tube and use the fine focus knob to focus focus the image 7-repeat 5 and 6 useing the x 40 objective lens
whats the resolution of a light microscope
200 nanometers
what sort of image is produced by a scanning electron microscope?
a 3D black and while image- a computer programme can add false colour.
what do electron microscopes use
a beam of fast travalling electrons with a wavelengthof about 0.004nm
what can be seen useing a light microscope
amoeba-1mm onion epidermis cell - 100 macometer (um) huan ovum and cheek cell - 50 macrometers mictochondrian , chloroplast, bacterium- 1 macromaters influenza virus- 100 nm
when phtographed what is priduced from an electon microscope?
an electron micrograph
what does the magnification of light microscopes enable us to see
can clearly see some of the larger structures inside the cell
what are laser scanning microscopes also known as?
confocal microscopes
what happends witha scanning electron microscope? (simply)
electrons are bounced of the surface of an object
wat happends with a transmission electon microscope? (simply)
electrons are passed through a thin specimin
what can be seen useing a electron microscope
everything that the lught microscope can see and: * ribosme and proteins -10 nanometer (nm) *lipids- 1 nm * an atom - 0.1 nm
what has to happen to the specimin with a transmission election microscope? how?
has to be chemically fixed by being dehydrated and stained
what can we say about the specimins used? why ?
have to be dead as placed in a vacuumand often coated with fine film of metal
health and safety when carrying a light microscope?
hold it by its arm in one of your hands while having your other hand under the base
where are laser scanning microscopes used (this is pretty much an advantage)
in the medical profession e.g. to observe fungal filaments within the cornea of the eye of a pateint with a fungal cornea infection- to give a swift and early disgonosis- and therefore treatment is more effective
what does this small wavelengh mean for electrom microscopes
its 125 000 times smaller than the central part of the visable light section they have a much greater resolution than optical microscopes and can be used to give clear and highly magnified images
what do optical (light) microscopes rely on
lenses to focus a beam of light
what sort of magnification do microscopes produce? what does this mean?
linear if a specimin is magnified x100- it appears to be 100 times wider and 100 times longer than it really is
what object can be seen in a transmission electron microscope?why?
living material as its done in a vacuum
whats an electron micrograph?
photograph of an image seen useing an electron microscope
whats the phtotograph that you see useing an optical microscope called?
photomicrograph
whats the advantages of a optical microscope
relively cheap easy to use portable and able to be used in the feild as well as in labatories able to be used to study whole living organisms
what organelles cant you see with a light microscope? why ?
ribosomes they are about 20nm in diameter proteins- 10-20 nm lipids- 1nm
define organelle
small structures within cells each of which has a specific function
what does the wavelengh to visable light mean for the images produced by light microscopes
structures closer together than 200nm will apear as one object
what is resolution?
the clarity of the image how clearly we can detinguish beetween two points. the higher the resolution the greater the detail and the clear the image
how do electron microscopes work
the electrons are fired from a cathode and focused by magnets (rather than glass lenses) onto a screen or photograpic plate
magnification defintion
the number of times larger an image appears compared with the size of the original object
why cant light microscopes magnify any higher while still giving a clear image?
their resolution is limited
what are the disadvantages of transmission electron microscopes
they are very large they are expensive they need a great deal of skill and training to use
what can we say about the specimins used by a laser scanning microscope
they can be living
what can we say about the images prduced by a laser scanning microscope
they have a high resolution and show high contrast
what are the features of a laser scanning microscope? what does this allow?
they have depth selectivity and can focus on structures at diffrent depths within a specimen. they can therefore be used to clearly observe whole living specimins as well as cells
how do laser scanning microscopes work?
they use laser light to scan an object point and point and then useing a computer they assemble the pixel information into one image displayed on a computer screen.
whats the calculation for magnification?
total magnification = magnifying of the objective lens x magnifying power of the eyepeice lens
what are the two types of electron microscopes
transmission electron microscope and scanning electron microscope
what magnification is is produced with a scanning electron microscope?
upto x200 000 (From x 15)
how does a scanning electron microscope work ?
uses a beam of electrons, these dont pass trough the sample, they bounce off and are picked up by the electron detector
what light do light microscopes use- whats the wavelengh of it?
visible light 400- 700 nm
what magnification can you get with a light microscope?
x1500 (sometimes x2000)
magnification of a transmission electron microscope?
x2,000,000 ( 2 million) one is being produced that can do x50,000,000 (5 million)