In a microscope, objects appear upside-down and backwards. If a specimen were to move forward and right, it would
appear to move backward and left when viewed through a microscope. The total magnification is found by multiplying the
magnification of the ocular and the objectives. For example, if the ocular of a microscope is 10x and the objectives are on
12x, the total magnification would be 10 times 12, which is 120x total magnification. On a normal microscope, the ocular is
usually 10x or 12x, while the objectives are about 5x for scanning, 10x or 12x for low power, and 40x-45x for high power.
When changing objectives to a higher power/magnification (scanning to low to high), the size of the field of view decreases
and the field of view gets darker. The resolution (sharpness of image) and size of the image increase. The working distance
decreases and the depth of focus is reduced.
Ocular: This part of a microscope magnifies the image formed by the objectives. It is the part where the viewer looks
through to see the image. Nosepiece: Holds the objectives and is located below the arm and the body tube. Base:
Supports the microscope and acts as a foundation. Objectives: Lenses that form the first image (before the ocular) by
receiving light from the field of view. Arm: Connects to the base and holds up the ocular, body tube, objectives, and
nosepiece. Body Tube: The tube between the ocular and the nosepiece/objectives. Coarse adjustment: Used to adjust
the microscope in lower power. Fine adjustment: Used to adjust the microscope in high power or for fine tuning. Stage:
Supports the slide and specimen when being viewed. Stage clips: Clips on the stage that hold the slide in place.
Illuminator: A source of light, usually located below the stage. A lumarod (rod that collects light) is sometimes used as a
source of light in microscopes that do not use electric power. Diaphragm: Controls the amount of light reaching the
specimen.
Optical Microscope: Optical microscopes use visible light (or UV light in the case of fluorescence microscopy) to sharply magnify the samples. The light rays refract with optical
lenses. The first microscopes that were invented were found to belong in this category. Optical microscopes can be further subdivided into several categories: Compound
Microscope: The compound microscope is built of two systems of lenses for greater magnification (an objective and an ocular: eyepiece). The utmost useful magnification of a
compound microscope is about 1000x. Stereo Microscope (dissecting microscope): The stereo microscope is an optical microscope which magnifies up to about maximum
100x and provides a 3-dimensional view of the specimen. Stereo microscopes are highly useful for observing opaque objects. Confocal Laser scanning microscope: Unlike
compound and stereo microscopes, Confocal Laser scanning microscopes are reserved for research organizations. Such microscopes are able to scan a sample in depth, and
a computer can then assemble the data to create a 3D image. Electron Microscope: Electron microscopes are the most advanced microscopes used in modern science.
Modern electron microscopes use accelerated electrons that strike any objects in path, to magnify them up to 2 million times due to the very small wavelength of high energy
electrons. Electron microscopes are designed specifically for studying cells and small particles of matter, as well as large objects. The high energy electrons are quite tough on
the sample being observed. Because of the much shorter wavelength, the electron microscope has a higher resolving power than a light microscope. To reveal the structure of
objects, it may initially require a long time to completely dehydrate and prepare the specimen; a sleek layer of a metal can be used to coat some of the biological specimens for
easy observation. Scanning Electron Microscope: Scanning Electron Microscopes are characterized by lower magnifying power, but can provide 3-dimensional viewing of
objects. The Scanning Electron Microscope captures the image of the object in black and white after being stained with gold and palladium. Reflection Electron Microscope:
Reflection electron microscopes are also designed on the principle of electron beams, but they are characteristically different from transmission and scanning electron
microscopes being that it is built to detect electrons that have been scattered elastically. X-ray Microscope: An X-ray microscope uses a beam of x-rays to create an
unparalleled high-resolution 3D image. Due to the small wavelength, the image resolution is higher as compared to optical microscopes. The greatest useful magnification is
therefore also higher and it lies between the optical microscopes and electron microscopes. X-ray microscopes hold significant importance in science and research and have
one special advantage over electron microscopes: it allows observing the structure of the living cells. It is adept at slicing together thousands of images to generate a single 3D
X-ray image. Scanning Helium Ion Microscope (SHIM or HeIM): Scanning Helium Ion Microscopes are a new imaging technology which uses a beam of Helium ions beams
to generate an image. This technology has several advantages over the traditional electron microscopes; one advantage lies in the fact that the sample is left mostly intact (due
to the low energy requirements) and that it provides a high resolution. Scanning acoustic microscope (SAM): Scanning acoustic microscopes use focused sound waves to
generate an image. An acoustic microscope has a wide range of applications in materials science to detect small cracks or tensions in materials. The scanning acoustic
microscope is a powerful tool which can also be used in biology to study the physical properties of the biological structure and help uncover tensions, stress and elasticity inside
the biological structure. Neutron Microscope: Still under an experimental stage, Neutron microscopes generate a high-resolution image and may offer better contrast than
other forms of microscopy. The new technology would use neutrons instead of beams of light or electrons to generate high-resolution images. Scanning Probe Microscopes:
Scanning Probe Microscope helps visualize individual atoms. The image of the atom is computer-generated, however. It provides the researchers with an imaging tool for the
future where a small tip measures the surface structure of the sample. These specialized microscopes provide high image magnification to observe three-dimensional
specimens. If an atom projects out of the surface, then a higher electrical current flows through the tip. The amount of current that flows is proportional to the height of the
structure. A computer then assembles the position data of the tip. An enhanced 3D image is generated. A bright field microscope is one of the most widely used microscopes.
The image is darker than the illuminated field and is made by transmitting light through the specimen. A dark field microscope is similar to the bright field microscope but
instead of a dark image on a light illuminated field, the image is bright on a dark illuminated field. A bright field microscope can be adapted into a dark field microscope by adding
a stop to the condenser. A phase contrast microscope can be used with live specimens and produces an image where the specimen contrasts with a gray background. It can
be used to view internal cell details. A differential-interference microscope produces a colorful three-dimensional image and has two prisms which add contrasting colors to
the image. A transmission electron microscope (TEM) uses electron beams to form the image. It can magnify images up to 100,000X and works by transmitting electrons
through the specimen. A fluorescence microscope uses ultraviolet light to make the image which comes out as a colored image against a black field. A confocal microscope
also uses ultraviolet light to make the image.
Acellular Microbes - Prions: Prions (proteinaceous infectious particles) are infectious proteins that are responsible for a class of diseases known as the Transmissible
Spongiform Encephalopathies, which are neurodegenerative diseases including Mad Cow Disease and Kuru. Prions destroy the tissue of the nervous system, forming holes in
the brain and nervous systems. Prion diseases all involve modification of the prion protein, a normal part of mammalian cells. They are also all fatal and rapidly progressive. Like
viruses, prions cannot replicate on their own and rely on other organisms. Unlike other microbes, prions do not contain nucleic acids. Prions are thought to have originated from
ZIP proteins. Viruses: Viruses are microorganisms much smaller than bacteria that invade other cells in order to replicate. Viruses are responsible for a variety of diseases,
such as chicken pox. The origin of viruses is unclear; some may have come from plasmids (pieces of DNA that can travel between cells) or transposons (pieces of DNA that can
move themselves to different places in a cell's genome) while others may have evolved from bacteria.Some viruses, known as bacteriophages, infect bacteria. Their appearance
is often compared to that of an alien landing pod. Typically,their genome is composed of DNA rather than the RNA of retroviruses. Other viruses, most famously Sputnik, infect
other viruses. These are known as virophages. Viruses can be caused by either lytic or lysogenic infections. In a lytic infection, the virus injects its genome into the host cell,
which cannot differentiate between viral DNA and its own DNA. The cell begins to make mRNA from the viral DNA, which is then made into viral proteins that destroy the cell's
DNA. When the cell eventually shuts down, the virus continues to use the cell to replicate. Enough viruses are made to cause the cell to burst, or lyse. Hundreds or thousands of
released viruses then go on to infect other cells. In a lysogenic infection, a virus integrates its DNA into the host cell's DNA. This viral DNA is known as a prophage. The
prophage remains dormant in the cell's DNA for several generations before becoming active, leaving the cell's DNA, and directing the synthesis of new viral proteins. HIV, which
causes AIDS, is a lysogenic virus. Cellular Microbes - Bacteria: Bacteria are single-celled, prokaryotic microorganisms. Some bacteria are beneficial to humans while others
are pathogenic, but a majority of bacteria are harmless to humans. Pathogenic bacteria are responsible for a variety of diseases including strep throat and tetanus. Bacteria
come in 3 shapes: coccus(circular), bacillus (rod-shaped), and spirillum (spirally). Bacteria originate from the single-celled organisms that were the first to inhabit the Earth.
Organisms are often classified by their source of energy and source of carbon. Bacteria may be photoautotrophic, utilizing photosynthesis to produce food and oxygen and
using carbon dioxide as their source of carbon. This category includes purple and green sulfur bacteria. They may also be chemoautotrophic, making food using the energy from
chemical reactions and using carbon dioxide as their source of carbon - these bacteria serve an important role in the nitrogen and sulfur cycles. The two other types are
photoheterotrophs (including purple and green non-sulfur bacteria) and chemoheterotrophs (including most bacteria, animals, fungi, and protozoa). Motile bacteria may utilize
rotating flagella to move, or they may secrete slime to slide around like a slug. Bacteria may also be non motile. Archaea: Archaea are a group of single-celled microorganisms
that were previously thought to be bacteria. Archaea are prokaryotes. Their origin and potential for causing disease are currently unclear; however, archaea are thought to be
ancestors of eukaryotes or very close descendants because of their many similarities, including genes and inclusion of enzymes in translation and transcription processes.
Unlike bacteria, no known species of archaea form spores. Archaea are capable of living in extreme habitats and anaerobic environments. They are extremely tolerant to heat,
