Microscopy

From CreationWiki, the encyclopedia of creation science

Scanning Electron Micrograph of Snow Crystal

Microscopy is any of a number of techniques that use instruments, which produce images too small to be seen with the naked eye. Microscopy is typically used in microbiology and cell biology, but also in the investigation of the microstructures of metal or other materials. Using microscopic techniques, the intelligent design inherent within the created world becomes clearly evident.

The word microscope comes from the Greek words micron meaning "small" and scopos which means "aim".

1 Optical Microscopes
2 Electron Microscopes
3 History of Microscopy
4 References
5 External links
6 See Also

Optical Microscopes

Compound Optical Microscope

Optical microscope image of onion cells - 100X magnification

Compound optical microscopes can magnify an image up to 1000X, but have a very limited depth of field. Therefore, they are typically used to examine smears, squashed preparations, or a thinly sectioned slice of some material. An optical microscope involves passing light through a series of lenses, to be detected directly by the eye. The maximum resolution that one can image is determined by the wavelength of the photons that are being used to probe the sample; nothing smaller than the wavelength being used can be resolved. Visible light has wavelengths of 400-700 nanometers; larger than many objects of interest.

Typically, on a standard compound optical microscope, there are three objective lenses: a scanning lens (4X), a low power lens (10X), and high power lens (40X). Advanced microscopes often have a fourth objective lens, called an oil immersion lens that involves placing a drop of oil on the cover slip, and then immersing the objective in the oil. An oil immersion lens usually has a power of 100X. The actual power or magnification is the product of the powers of the ocular (eyepiece), usually about 10X, and the objective lens being used.

Electron Microscopes

Main Article: Electron microscope

Scanning Electron Microscope

SEM image of the Rust Mite (Aceria anthocoptes) - magnified 1,400X.

An electron microscope is an electron-optical instrument in which a beam of electrons is used to produce an enlarged image of a minute object on a fluorescent screen or photographic plate. Electron microscopy is used when items or features are too small to be imaged by light. In this case, the image is created by the bending/reflection of an electron beam rather. It can magnify very small details with high resolving magnifying at levels up to 500,000 times.

Scanning Electron Microscope (SEM) - is used to produce images with a characteristic three-dimensional quality. The method is for determining the surface structure of a solid by measuring the angle and energies of electrons scattered by the atoms on the surface of a sample.

Transmission Electron Microscope (TEM) - is much like that light microscope, but generates in image by sending an electron beam through a very thin slice of the specimen. The resolution limit is around 0.05 nanometer.

History of Microscopy

Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia (1655), which is the origin of the word "cell"

The origin of the microscope is a matter of debate, but many give credit to the Dutch spectacle-maker Zacharias Janssen for inventing the first compound microscope in the late 1500s. Galileo Galilei further improved upon the technology in the year 1609, by designing one with a convex and concave lens. The phase contrast and electron microscopes were both first invented in the 1930s. The phase contrast microscope was developed by the Dutch physicist Frits Zernike for which he was awarded the Nobel Prize in 1953. The first transmission electron microscope was built by Ernst Ruska.^[1]