Microscopy Flashcards
What is the most important tool for studying microorganisms?
The light microscope
What is the most common light microscope? What does it illuminate?
The bright-field microscope evenly illuminates the entire field.
To what degree can a bright-field microscope magnify a specimen? What is the cause of the limitation?
Bright-field microscopes can magnify specimen up to 1000x. [100x objective, 10x ocular.] It is limited by the wavelength of visible light.
What are the 3 most important factors in light microscopy?
- Magnification 2. Resolution 3. Contrast
How many lenses does a compound microscope have? What are their names?
2 lenses: objective and ocular.
What is the purpose of the condenser lens?
It is used to focus the illumination on the specimen.
What is resolution, with regards to light microscopy?
Resolving power is the minimum distance existing between two objects when those objects still appear as separate objects.
What are the variables that resolution depends upon?
- Quality of lens 2. Wavelength of illuminating light.
How is resolution enhanced at an objective magnification of 100x? How does it work?
Immersion oil reduces light refraction. Oil has nearly the same refractive index as glass, so light does not bend away from the objective lens in the small space between the specimen and objective lens.
What is the maximum resolving power of most bright-field microscopes? What can be seen? What is too small to see?
The resolving power is 0.2μm, which is small enough to see bacteria, but not viruses.
What do electron microscopes require to produce an image?
Electromagnetic lenses, electrons, and a fluorescent screen
What is the magnification of an electron microscope?
100,000x 0.3 nm (3 x 10^-10)
What are the two types of electron microscopes? What does each type do?
Scanning (SEM) shoots e- from the side of the prepared specimen to reveal surface detail. It is then artificially colored. Transmission (TEM) shoots e- through the specimen, like a bright-field microscope, to allow observation of fine detail.
What is contrast, with regards to microscopy?
Contrast reflects the number of visible shades in a specimen.
How can higher contrast be achieved?
- Light control 2. Special microscopes 3. Staining
