studying cells Flashcards
-> microscopes, cell fractionation + ultracentrifugation
what is magnification equation?
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A M
how do light microscopes work?
they pass a beam of light through a thin sample
- use glass lenses to focus images
what is magnification?
how enlarged an image is
what is resolution?
the minimum distance apart that two objects can be distinguished as separate objects
advantages of optical microscopes
- cheap
- produce colour images
- easy to use
- can view live specimens
disadvantages of optical microscopes
- low resolution
- low magnification
- specimens must be thin
- stains required
Why do electron microscopes have a higher resolution than a light microscope?
as electrons have a shorter wavelength than the wavelength of light
total magnification equation
objective magnification x eyepiece magnification
how do electron microscopes work?
use a beam of electrons in which pass through/over the surface of a sample
why are EM greyscale?
- some areas absorb electrons more than others
- heavy metal stains are used
why must EM specimens be dead?
as they are viewed in a vacuum
how are TEM images made?
by passing a beam of shorter wavelength electrons through a sample, creating 2D images
how are SEM images made?
by passing a beam of shorter wavelength electrons across the surface of a sample, creates 3D images
advantages of EM
- high resolution so can view smaller organelles
- high magnification
disadvantages of EM
- more complex + expensive
- greyscale images
- artefacts common
- specimens must be dead
