Microscopes Flashcards
What are the principles of a light microscope ?
-long wavelength light shone on specimen
What can you see with a light microscope?
Nucleus
Nucleolus
Cell membrane
Cytoplasm
Advantages of a light microscope
-colour images can use living samples
Disadvantages of a light microscope
-lower resolution due to long wavelength of light
lower magnification
-smaller organelles in cells are not visible
-max magnification is x1500
-max resolution is 0.2 micrometers
What are the principles of a scanning electron microscope?
-scans electrons across surface of objects
-knocks of electrons which are gathered by cathode to form
What can you see with a scanning electron microscope?
Surface of a specimen eg shape of cell
Advantages of an SEP
Higher magnification
Higher resolution
Details on image (texture and 3d depth )
Thick specimens
Disadvantages of an SEP
[samples must be in a vacuum ]
Lower resolution than TEM(20nm)
What are the principles of a transmission electron microscope?
Beam of electrons focused by electromagnet
Some parts absorb elements and appear dark
Extremely thin specimens
What can you se with a TEM?
Chloroplasts,mitochondria ,Golgi, E.R, ribosomes ,lysosomes, cell wall
Advantages of a TEM
Higher resolution than light microscope due to shorter wavelength of electron beam
Disadvantages of TEM
Need a vacuum so can’t view living specimens
Complex staining process
Black and white image
Very thin specimens needed
Image contains artefact
Define magnification
How many time larger rhe image is compared to the object
Define resolution
Minimum distance between two objects in which they can still be wirewed as separate
