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)