Electron Microscope👩🏾🔬 Flashcards
Why do electron microscope show a clearer, more detailed image than light?
Higher resolution and magnification due to the electron beam having a shorter wavelength than light.
How does the TEM works?
*inside,w and b,high resolution and magnification
-beam of electron passed through the specimen
-Denser parts absorb more electrons so it is darker
-darker=denser (have more structure within them) so they are visible
-scattered electrons are then captured on photographic plate.
-2D
-magnification up to 250,000 times
-resolution for biology = 2nm
How does an SEM work?
-specimen coated in thin layer of metal
-beam of electrons focused by electro magnet
-beam of electrons is bounced off the surface onto photographic plate
-allows 3D images to be built by a computer
-magnification-100,000
-Resolution- 3-20 nm
What is an artefact?
-An object in image which is not part of the specimen
-fault due to specimen preparation
E.g dust air fingerprint
What does the magnet in condenser in a TEM do?
Focuses the beam (opposing charges)
Give me the advantage of electron microscope?
Higher resolution due the electron beam wavelength wavelength shorter than light(*2000 higher resolution than light microscope) so smaller organelles can be seen (ribosome,lysosomes,R/SER)
-SEM produces 3D images
Limitations of electron microscope?
Both:must be in a vacuum-(no living specimen can be observed)
-Image is black and white
-complex staging process so image may contain artefacts
TEM:specimen must be very thin to allow the electrons to penetrate,so flat 2D image can be overcome by taking a series of sections
-SEM: lower resolving power
Than TEM but still better than light
Why is a vacuum necessary inside the body of an electron microscope?
-Electrons are deflected when they strike gases in air so it difficult for electron beam to focus
-a vacuum solves this problem
How is an image brought in focus in a TEM compared with light microscope?
TEM:has magnets
Light microscope has glass lenses
