Microscopy Flashcards
What is magnification?
How zoomed in an image is.
What is resolution?
The sharpness of an image, how easily you are able to distinguish between 2 points on a photomicrograph.
How do light microscopes produce images?
A microscope that uses light and lenses to produce images.
What type of tissue do light microscopes view?
Living.
Describe the how the wavelength of light affects the images produced by light microscopes.
Light has a long wavelength.
This means the resolution is low, so images may not be as clear.
Describe the magnification and resolution of light microscopes.
Low magnification
Low resolution
Describe the magnification an resolution of electron microscopes.
High resolution.
High magnification
What is used to fire electrons at specimens when a TEM is used?
An electron gun.
How is the beam of electrons focused on the specimen for a TEM?
A condenser electromagnet focuses the beam onto the specimen.
Describe what a photo micrograph produced by a TEM would look like.
Darker areas of the image will be due to absorbance of electrons.
Lighter areas of the image will be due to transmission of electrons.
The image is in black and white.
Why must specimens for TEM be dead?
The system is in a vacuum, therefore they would not be able to survive.
Why are metals such as gold used when using TEM?
They aid with the scattering of electrons.
Describe the differences in what can be seen by SEM and TEM.
SEM - 3D image of the surface of a specimen
TEM - 3D image of the inside the cell, and inside some organelles.
State what SEM use to produce images.
Lasers/high powered beams of light.
How do SEM produce 3D images?
They take several 2D photos and combine them to make a 3D image.
Describe the photomicrograph produced by a SEM.
A black and white image that shows the surface of the specimen. (Not inside the specimen)
Why doesn’t the specimen need to be thin when using a SEM?
Electrons scan the top surface of the specimen only, they do not need to penetrate.
Compare the cost of light microscopes and electron microscopes.
Optical microscopes are much cheaper than electron microscopes.
State whether the images produced by each of the microscopes are 3D or 2D.
Light - 2D
SEM - 3D
TEM - 3D
Describe the drawbacks of the complex staining process for electron microscopes.
The staining process is complex.
This is a drawback because the photomicrograph produced is black and white anyway.
What are artefacts?
Anything not apart of the specimen that could result in a change in the image from the way the specimen is prepared.
Give the formula for magnification.
Image size / Actual size
