m3 module 3 exam graded a essential microbiology with lab | portage learning
resolution and contrast are two critical factors that influence your ability to see an objec
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Exam 3
. A nanometer is defined as:
A. 10-3
B. 10-6
C.10-9
D. 10-12 C. A nanometer is defined as one-billionth of a meter.
2. True or False: A nanometeris longer than a micrometer. False. A nanometer is 1,000 times
smaller than a micrometer.
1. Resolution and contrast are two critical factors that influence your ability to see an object. Explain
each. 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.
*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).
1. Assuming a constant (non-adjustable) light source power, identify the part of the microscope you
would adjust to limit the amount of light entering the microscope.
Select all that apply.
A. Objective
B. Condenser
C. Iris diaphragm
D. Eye piece
C. The iris controls the amount of light that passes through the sample and into the objective
lens. Thus, it can be adjusted (opened or closed) to alter the amount of light.
2. What is the total magnification (relative to your eye) of a sample imaged with a 60x objective and
a 10x eyepiece? Show your math. 60 x 10 = 600x magnification
1. True or False: Staining is often required to image a cell that is adherent and flat (thin). True.
Adherent, flat and unstained cells are almost invisible due to the limits on both resolution
and contrast. Therefore, cell staining is often required to adequately image the sample.
2. Which of the following could NOT be seen clearly by the unaided eye? Select all that apply.
A. Bacteria with diameter of 24 μm
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