Portage Learning Microbiology Exam 3
1. A micrometer is defined as: 10^-6
2. Resolution and contrast are two critical fac- Resolution: The ability to see two objects as
tors that influence your ability to see an separate, the lower resolution may cause
object. Explain each. two objects to appear as one
Contrast: The amount of light absorbance
between two objects, for example, between
the specimen and background. Lower con-
trast may make it more difficult to differen-
tiate the specimen from the background
3. Assuming a fixed ocular, identify the part C) Objective
of the microscope you would adjust to en-
hance the magnification of a sample.
A) Condenser
B) Iris Diaphragm
C) Objective
D) Eye Piece
4. What is the total magnification (relative to Objective lens x ocular eyepiece = total
your eye) of a sample imaged with a 20x magnification
objective and a 15x eyepiece? Show your
math. 20x objective x 15x eyepiece = 300x magni-
fication
5. True or False: A cell that is adherent, flat False, flat cells are almost invisible due to
(thin), and unstained is easily identified us- the limits on both resolution and contrast
ing bright field microscopy.
6. Which of the following could NOT be seen -Bacteria with diameter of 24 μm
clearly by the unaided eye? Select all that -Virus with a diameter of 0.2 μm
1/6
, Portage Learning Microbiology Exam 3
apply.
-The unaided eye can, on average, clearly
-Protozoa with diameter of 250 μm resolve objects > 200 μm
-Skin cell with diameter of 1500 μm
-Bacteria with diameter of 24 μm
-Virus with a diameter of 0.2 μm
7. Label the following unmarked microscope
components (numbered arrows) by match-
ing it with the components provided (let-
ters).
A. Stage
B. Fine Adjustment Knob
C. Iris Diaphragm
D. Neck
E. Condenser Lens
F. Eyepiece
G. Objective
H. Base
I. Coaxial Controls
8. This type of microscope utilizes ultraviolet Fluorescence
(UV) light to illuminate stained objects.
9. This type of microscope uses a special- B) Phase-contrast
ized condenser and objective to amplify the
slight differences between cells and back-
ground.
A) Dark Field
B) Phase-contrast
2/6
1. A micrometer is defined as: 10^-6
2. Resolution and contrast are two critical fac- Resolution: The ability to see two objects as
tors that influence your ability to see an separate, the lower resolution may cause
object. Explain each. two objects to appear as one
Contrast: The amount of light absorbance
between two objects, for example, between
the specimen and background. Lower con-
trast may make it more difficult to differen-
tiate the specimen from the background
3. Assuming a fixed ocular, identify the part C) Objective
of the microscope you would adjust to en-
hance the magnification of a sample.
A) Condenser
B) Iris Diaphragm
C) Objective
D) Eye Piece
4. What is the total magnification (relative to Objective lens x ocular eyepiece = total
your eye) of a sample imaged with a 20x magnification
objective and a 15x eyepiece? Show your
math. 20x objective x 15x eyepiece = 300x magni-
fication
5. True or False: A cell that is adherent, flat False, flat cells are almost invisible due to
(thin), and unstained is easily identified us- the limits on both resolution and contrast
ing bright field microscopy.
6. Which of the following could NOT be seen -Bacteria with diameter of 24 μm
clearly by the unaided eye? Select all that -Virus with a diameter of 0.2 μm
1/6
, Portage Learning Microbiology Exam 3
apply.
-The unaided eye can, on average, clearly
-Protozoa with diameter of 250 μm resolve objects > 200 μm
-Skin cell with diameter of 1500 μm
-Bacteria with diameter of 24 μm
-Virus with a diameter of 0.2 μm
7. Label the following unmarked microscope
components (numbered arrows) by match-
ing it with the components provided (let-
ters).
A. Stage
B. Fine Adjustment Knob
C. Iris Diaphragm
D. Neck
E. Condenser Lens
F. Eyepiece
G. Objective
H. Base
I. Coaxial Controls
8. This type of microscope utilizes ultraviolet Fluorescence
(UV) light to illuminate stained objects.
9. This type of microscope uses a special- B) Phase-contrast
ized condenser and objective to amplify the
slight differences between cells and back-
ground.
A) Dark Field
B) Phase-contrast
2/6
