Microscopy Flashcards
What is Resolution?
The smallest separation at which two objects can be distinguished (smallest unit of measurement)
How is the resolution of a microscope limited and how can that limitation be circumvented?
Limited by the wavelength of visible light. By using a shorter wavelength of light, the resolution can be further improved.
How do light microscopes work?
Specimens are illuminated with light which is focused using glass lenses and viewed with the eye or a photographic film. Specimens need to be coloured with stain in order to be visible.
What are the types of light microscope?
- Transmission Microscopes
- Fluorescence Microscopes
- Interference Microscopes
- Confocal Microscopes
What is a transmission microscope?
Light is transmitted through the specimen is focused to form an image. Can see cells and tissues, but not cell organelles.
What is a fluorescence microscope?
Uses fluorescent dye to stain specimens. Illuminated with ultraviolet radiation, so stained objects emit visible light. More precise than transmission.
How do Electron Microscopes work?
This uses a beam of electrons instead of light to illuminate the specimen. Electrons can be used to resolve small sub cellular ultrastructure.
What are the problems with electron microscopy?
- Requires a vacuum, so cannot be used for living organisms
- Electron beam can damage some specimen
- Specimen cannot be manipulated because they must be embedded in plastic because they are so thin.
- Specimen must be stained with electron dense chemical
What are the two kinds of electron microscope?
- Transmission Electron Microscopes
- Scanning Electron Microscopes
How does a Transmission Electron Microscope work?
A beam of electrons is transmitted through a specimen and focused to form an image on a screen or a film. Has the best resolution.
How does a scanning electron microscope work?
They scan a fine beam of electrons onto a specimen and collect the electrons scattered on the surface. Gives poorer resolution but better 3D Imaging.
What is Magnification?
Magnification indicates how much bigger the image is than the original object. Usually given as a magnification factor. e.g. X100
