Microscope Flashcards
Maginification
Size of image / size of real object
What are the two types of microscope
Transmission electron microscope and the scanning electron microscope
What is the resolving power of TEM
0.1nm
Why cant the resolving power always be reached when using a TEM
Difficulties preparing the specimen can limit the resolution that can be acheived
Higher energy electron beam is required and this could destroy the specimen
The electron gun in a transmission electron microscope produces…
A beam of electrons
The beam of electrons in a TEM is…
Focused onto the specimen by a condenser electromagnet
When using the TEM does the beam of electrons pass through the specimen or pass over it?
The beam of electron in a TEM passes through the specimen
Why do parts of specimen appear darker whenusing TEM
Parts of the specimen appear darker when observed throuhg TEM because the specimen absorb electron
Why do parts if specimen appear lighter when using TEM
Parts of the specimen appear lighter when observed through a TEM because the electrons pass through the specimen rather then the specimen absorbing it
Name three limitation of the transmission electron microscope
- Living specimen cannot be observed using the TEM because the whole microscope must be in a vacuum
- You have to carry out a complex staining process in order for the image to be seen (even then it is not in colour)
- The specimen used has to be extremely thin. The image may contain artefact which may lead to false result
How can we build a 3D image using a TEM
When using a TEM, the specimen has to be really thin to allow electrons to penetrate it therefore a 2d image is produced . To obtain a 3D image you would have to take a series of photomicrograph and then combine togther
What is a photomicrograph
A photograph of a microscope object, taken with the aid of a microscope
In which direction does the beam of electrons come from when using a TEM
The beam of electrons come from undermeath the specimen
In which direction does the beam of electron come from when using a SEM
The beamof electron come from above the specimen
Where is the beam of electron directed eithin a SEM
The beam is directed back and forth across a portion of the specimen on a regular pattern
TEM stands for..
Transmission electron microscope
SEM stands for…
Scanning electron microscope
What does the contouring of the specimen surface depend on
The contouring of a specimen surface depend on how the electron are scattered by the specimen
What is the resolving power of the SEM
20nm
How can a 3D image be produced of the specimen when using a SEM
A 3D image can be built on a computer when the pattern of the scattered electrons is analysed and secondary electrons are produced