what is an SEM microscope?
scanning electron micropscope
outline how a SEM works
- beam of electrons projected across specimen surface and reflected electrons are collected
- allows details images of surface features
- produces 3D, B&W image
what is a TEM microscope?
transmission electron microscope
outline how a TEM works
- beam of electrons transmitted through specimen and focused to produce an image
- generates image of internal features
- 2D, B&W image:
- darker = fewer electrons passed through,
- lighter = more electrons passed through
describe what a microscope does
enables magnification of an object many times in order to observe structures/organisms which are impossible to see with a naked eye
name 4 different types of microscope
- light microscope
- transmission electron microscope (TEM)
- scanning electron microscope (SEM)
- confocal laser scanning microscope (CLSM)
what is the function of the eyepiece lens?
- the lens the viewer looks through
- usually contains a 10X or 15X power lens
outline how a laser scanning confocal microscope works
- specimen is treated with fluorescent chemical to illuminate/highlight specific structures
- single spot of focused light of a specific wavelength is moved across specimen
- fluorescence from the components labelled with dye is caused
- emitted light is filtered through pinhole aperture
- only light radiated from very close to the focal plane is detected
how does a light microscope work?
light from a light source under the stage passes through the specimen
what is the resolution of a light microscope?
200nm
what is the magnification of a light microscope?
x1500
what type of image is produced by light microscopes?
- colour image
- 2D
what is a strength of light microscopes?
can use live specimens
what is a weakness of light microscopes?
poor resolution
what is the resolution of a TEM?
0.5nm
what is the magnification of a TEM?
x1,000,000
what is a strength of a TEM?
good resolution
what is a weakness of a TEM?
specimens must be dead
what is the magnification of SEMs?
x500,000
what is the resolution of SEMs?
2nm
how is magnification calculated?
image size / actual size
define resolution
the ability to distinguish between two separate points
define magnification
how many times bigger the image of a specimen observed is in comparison to the actual size of the specimen
how do convert cm to nanometers
1cm x10 = 10mm
10mm x1000 = 1micrometer
1micrometer x1000 = 1nm
