Microbiology Lab Chapter 5

kylerigonan's version from 2016-01-31 06:40


Question Answer
Anton van Leeuwenhoek1673 published his observations of what he termed "animalcules" (protozoa) that he made using his hand-made, single-lends microscopes that could magnify a specimen up to 270X
What is magnification?magnification is the process of enlarging an object's apparent size and results when light refracts(bends) as it travels through a curved lens
When referring to the magnifying ability (power) of a lens, how is magnification defined?Defined as the ratio of the object's apparent size when viewed through the lens compared to how the object would appear to the naked eye at a distance of 25 cm.
How is the magnifying ability of a compound microscope found?Product of the magnification power of the ocular (eyepiece) lens and the power of the objective lens.
What does resolution refer to?refers to a lens's ability to distinguish between objects that are close together, thereby allowing the lens to reveal fine detail.
The better a lens's resolving power, then the closer together objects can be and still be distinguished as separate.
What does a lens's resolving power depend on?1) the wavelength of the light being passed through the lens 2) the numerical aperture of the lens 3) the quality of the lens
what is numerical aperture(NA)? The lens's ability to gather light
what does a lower Refractive Index indicate?lower Refractive Index means that light bends more than if it was higher
What is oil immersion?Improve the lens's resolving power by using oil (RI=1.52) between the specimen and the lens. Used only with 100X
What is field of view or field?is the area that can be viewed at one time through a given objective.
As the magnifying power of a objective lens decreases the size of the field of view will ______decrease
Increasing the lens power will _____ the depth of the field. decrease
what is the eyepiece of ocular?the part you look through to view a specimen. Usually contains a 10X lens.
what is the arm of a microscopeconnects the oculars to the rest of the microscope. When carrying a microscope, one grasps the arm with one hand, and supports the base with other.
The nosepiece of turret of a microscope?holds the various objective lenses. The nosepiece revolves to allow the use to switch from lens to lens
The objective or lens is used for what?to magnify a specimen for examination
what does it mean when stated the objectives of the microscope are parfocal?Objectives are focused relative to each other. When an object is in focus in one objective, only minor adjustments will be needed to bring the object into focus with another objective
what is the condenserfocuses the light onto the specimen. Condenser can be raised and lowered to adjust the amount of light passing through the specimen. You can also adjust the amount of light passing through the specimen by opening and closing the condenser's iris diaphragm
coarse adjustment knobraises and lowers the stage in large increments to allow the user to focus the specimen. Coarse adjustment should only be used when focusing the 4X and 10X objectives
Fine adjustment knobraises and lowers the stage in very small increments, and is used when focusing the 40X and 100X objectives
The lamp or light sourceprovides the light that will pass through the specimen, enabling the user to view the specimen
Rheostatallows the operator to adjust the lamp's output. Turn rheostat to increase the amount of light when going from lower to higher magnifications. When putting the microscope away at the end of the class, the rheostat should always be "1" (or to the lowest setting) to avoid blowing the lamp fuse
What is the on/off switch located?at the front of the microscope base
what is the base?provides a stable platform for the microscope. When carrying a microscope, one hand should support the base from beneath, while the other hand firmly grasps the arm.
What are the 3 controls that can be adjusted to determine the amount of light coming through the specimen?1) Iris diaphragm of the condenser (can be open and shut) 2) The condenser (can be raised and lowered) 3) rheostat