Microscopy, Staining, and Classification
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The use of light or electrons to magnify objects.
The change in speed of light , the denser the specimen, the slower light travels through. In this way, we can "weigh" a cell wall, or nucleus or a chloroplast, or even a single chromosome.
What are the general principles involved in both light and electron microscopy?
Wavelength of radiation, magnification of an image, resolving power of the instrument, and the contrast in the specimen.
The distance between two corresponding parts of a wave. Beams of radiation may be referred to as either rays or waves.
Negatively charged particles that orbit the nuclei of atoms. Moving electrons act as waves with wavelengths dependant upon the voltage of an electron beam.
What determines the degree to which the image is enlarged?
It depends on the thickness of the lens, its curvature, and the speed of light through its substance.
If a microscopist combined lenses to magnify millions of times, the image would be faint and blurry.
What properties determine the clarity of an image, which in turn determines the useful magnification of a microscope?
Resolution and contrast
Also called resolving power, is the ability to distinguish between objects that are close together. The better the resolution, the better the ability to distinguish two objects that are close to one another.
Refers to the differences in intensity between two objects, or between an object and its background.
What ways to increase the contrast between MO and their background?
To stain them, or when the use of light that is in phase (which when all waves' crests and troughs are aligned).
Where the background (or field) is illuminated.
The specimen is made to appear light against a dark background.
Use the alignment or misalignment of light waves to achieve the desired contrast between a living specimen and its background.
Use invisible ultraviolet light to cause speciments to radiate visible light, a phenomenon called fluorescence.
Use lasers to illuminate fluorescent chemicals in a thin plane of a specimen.
What are two different types of bright-field microscopes?
Simple and compound microscopes
Contains a single magnifying lens and is more similar to a magnifying glass than to a modern microscope.
Uses a series of lenses for magnification.
Who invented to compound microscope as early as 1590?
Galileo Galilei (1564-1642), but it was not until about 1830 that scientists developed compound microscopes that exceeded the clarity and magnification of Leeuwenhoek's simple microscope.
How is magnification achieved in a basic compound microscope?
Light rays pass through a specimen and into an objective lens, which is the lens immediately above the object being magnified.
A lens immediately above the object being magnified and is a series of lenses that not only create a magnified image, but are also engineerred to reduce aberrations in the shape and color of the image.
List the objective lenses on a typical microscope.
- Scanning Power: 4x
- Low Power: 10x
- High Power: 40x
- Oil Immersion: 100x
What does using the oil immersion objective lense increase?
Magnification and resolution. The oil enables the lens to capture more light rays to produce a clearer image because light does not refract.
The distance between the lens and the specimen.
The objective lens bends the light rays, which then pass up through one (monocular) or two (binocular). Ocular lenses magnify the image created by the objective lense, typically another 10x.
How do you calculate total magnification?
It is determined by multiplying the magnification of the objective lens by the magnification of the ocular lens.
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