MICROSCOPY AND SLIDE PREPARATION
- Created by: IzabellaStar
- Created on: 06-12-17 12:52
MICROSCOPY
The first type of microscopes that were developed were the light microscopes in the 16th and 17th century.
Microscopes allowed us to see cells for the first time and therefore scientists were able to conclude that all living things are composed of cells, that cells are the basic unit in life and that cells only develop from existing cells.
History of the Microscope
First glass experiments occurred during Roman era.
13th century - spectacles and eye glasses
15th century - Dutch spectacle makers invented telescope
17th Century - Galileo Galilei first true microscope
History of the Cell Theory
1665 - Robert Hooke observed thinly sliced cork and describe the structure as ‘Cells’
1674-1683 - First living cell observation.
1832- cell division in plants
1833 - nucleus observation
1837-1838 - all plant tissue made of cells
1844 - first observed animal cell division
1860 - Louis Pasteur disproved spontaneous generation
The cell theory was only able to develop when powerful enough microscopes were discovered. Many scientists didn't believe the cell theory before this because they couldn't see the cells. This all changed in the 19th century.
Resolution Power: the ability of a microscope to differentiate between two close together objects. A higher resolution means that the objects that are closer together can be seen as separate points. (can tell apart objects that are closer together. Resolution is limited by the diffraction of light. As light pases through a narrow gap the light waves have a tendency to spread out when they pass through a narrow gap. The structures present in a specimen are very close together and when the light reflects off them it can overlap due to diffraction. This causes them to NOT be seen as separate entities and detail is lost. Resolution can be increased using a beam of electrons instead as they have a much smaller wavelength.
Magnification: How much larger the image being viewed is compared to its actual size.
Light Microscope
The light microscope has been around for about the past 400 years allowing scientists to study the small details of everyday life.
The light microscope is one of the simplest types of microscopes and it consists of a stage which is used for holding the specimen, a light source that is located at the bottom of the microscope and is shone up toward the stage through a condenser lens which focuses the light , the objective lense that collects and focuses the light coming through the specimen and finally an eyepiece lense which magnifies the image. The image is then created from the fact that regions that absorb more light appear darker.
Scanning Electron Microscope
With scanning electron microscopes we use electrons instead of light. Electrons have a smaller wavelength and therefore we are able to get a higher resolution. However you don't look at the specimen directly. A computer forms an image based on how many electrons are absorbed by different regions of the specimen, as the electrons that are not absorbed are…
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