BIOD 171 Portage Learning Exam 3 Define the measurements micrometer and nanometer. - ANSWER-A micrometer is one-millionth of a meter and a nanometer is one-billionth of a meter. What are the two critical factors that influence your ability to see an object? - ANSWER-The resolution and the contrast....
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BIOD 171 Portage Learning Exam 3
Define the measurements micrometer and nanometer
A micrometer (µm) is defined as being one-millionth of a meter and is commonly designated at 10-6
meters. A nanometer (nm) equals 10-9 m or one-billionth of a meter.
What are the two critical factors that influence your ability to see an object?
Resolution and contrast. Resolution refers to the distance between two objects at which the objects still
can be seen as separate. Poor or low resolution means two (or more) objects may appear as one. The
contrast is the difference in light absorbance between two objects. Poor contrast gives a high
background and makes the visualization of multiple objects difficult. For instance, trying to identify 2
dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of a
sunny afternoon (bright light against 2 dark objects = high contrast).
If you wish to increase the amount of light going into a microscope, what part
would you adjust?
The iris diaphragm controls the amount of light that passes through the sample and into the objective
lens. Thus, as you open the iris more light is permitted to pass through to illuminate the sample.
As light passes through a microscope, what is the last piece that light passes
before reaching your eyes?
Once light passes through the sample and the objective lens it is directed through the ocular lens, or
eyepiece, directly into your eye.
How is the total magnification of an object calculated?
Total magnification is calculated by multiplying the power of the objective and the power of the
eyepiece. For instance, a 40x objective with a 10x eyepiece would make an object appear (40 x 10) 400
times larger (400x).
What is one limitation of fixing your sample?
Fixation requires you to irreversibly kill your sample. Thus, determining the motility (cell movement) of a
sample is impossible. Fixation also runs the risk of distorting the specimen shape and arrangement.
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