BIOD 171 EXAM MODULE 3

. A micrometer is defined as

• 10

-3

• 10

-6

C.10 -9

• 10

-12

• A micrometer is one-millionth of a meter.

2. True or False: A nanometer is longer than a micrometer.

False. A nanometer is 1,000 times smaller than a micrometer.

• 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).

• 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.

BIOD 171 EXAM MODULE 3

Exam Page 2 Answer Key

Exam Page 3 Answer Key

• True or False: A cell that is adherent, flat (thin) and unstained is easily identified using bright field

microscopy.

False. Adherent, flat cells are almost invisible due to the limits on both resolution and contrast.

• Which of the following could be seen clearly by the unaided eye? Select all that apply.
• Bacteria with diameter of 24 μm
• Protozoa with diameter of 150 μm
• Virus with a diameter of 0.2 μm
• Skin cell with diameter of 1500 μm

B and D. The unaided eye can, on average, clearly resolve objects > 100 μm

• Label the following unmarked microscope components (numbered arrows) by matching it with the

components provided (letters).

Exam Page 4 Answer Key

Exam Page 5 Answer Key Select all that apply.

• Objective
• Condenser
• Iris diaphragm
• Eye piece

• 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.

• 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

• Stage
• Fine Adjustment Knob
• Iris Diaphragm
• Neck
• Condenser Lens
• Eyepiece
• Objective
• Base
• Coaxial Controls

1F

2D

• For each of the following questions select from the list below the single best answer:

Phase-Contrast Dark Field Fluorescence Confocal

This type of microscope is best suited for visualizing GFP, RFP and YFP proteins.

Fluorescence

• This type of microscope can provide detailed images of live cells without staining.

Phase-Contrast

• This type of microscope is used to greatly increase the contrast between samples and background by

reflecting light off of the specimen.

Dark Field

• This type of microscope is capable of capturing images in multiple focal planes, rendering a

specimen in 3D

Confocal

Exam Page 6 Answer Key

Exam Page 7 Answer Key 3B

4G

5A

6H