Microscopes Flashcards
What are the main differences between light microscopes and electron microscopes?
An electron microscope has a much shorter wavelength
An electron microscope produces a B&W image
Electron microscopes have higher resolutions
You can see live specimen with a light microscope
What are the two types of electron microscope?
SEM AND TEM
What are the limitations of a TEM?
The whole system must be in a vacuum and living things cannot be observed
A complex staining process is required
The specimen is very thin
Image may contain artefacts
A 2D image is produced
What are artefacts?
Things that are not actually present in the specimen but arise due to an error during preparation.
What is the formula for Magnification?
M = Image / Actual
What is resolution?
The ability to distinguish between two different points that are close together.
Why do electron microscopes have a higher resolution?
They have a much smaller wavelength than light which means they can resolve things that are 0.1nm apart.
How does a SEM work?
The specimen is coated in heavy metals to improve conductivity, the electrons are reflected and scattered by the specimen producing a 3D image.
Why can the resolution of 0.1nm of a TEM not always be achieved?
There may be difficulty preparing the specimen, a high energy electron beam is required but this can destroy the specimen.
