1
University of Hawaii at Hilo – BIO172L Lab
Practical Examination Instructor: Terre
Hawkins | Academic Year 2026/2027.
Domain 1: Microscopy & Laboratory Techniques.
Q1. Multiple-Choice When using the compound light microscope in the BIO172L lab,
you switch from the 10× objective to the 40× objective. Which of the following correctly
describes the change in working distance and field of view?
A. Working distance increases and field of view increases
B. Working distance decreases and field of view increases
C. Working distance decreases and field of view decreases
D. Working distance remains constant and field of view decreases
Correct Answer: C
Rationale: [CORRECT] As magnification increases from 10× to 40×, the working
distance (the space between the objective lens and the specimen) decreases, requiring
careful focus adjustment to avoid crushing the slide. Simultaneously, the field of view
decreases proportionally because higher magnification reveals a smaller area of the
specimen. This inverse relationship between magnification and field of view is
fundamental to microscope operation in introductory biology labs.
Q2. Multiple-Choice Which component of the compound light microscope is
responsible for concentrating and directing light onto the specimen?
A. The diaphragm
B. The condenser
, 2
C. The ocular lens
D. The coarse adjustment knob
Correct Answer: B
Rationale: [CORRECT] The condenser sits below the stage and gathers light from the
illuminator, focusing it into a cone of light that passes through the specimen. Proper
condenser adjustment (often paired with diaphragm regulation) is essential for
achieving maximal resolution and contrast when viewing wet mounts of Elodea or onion
epidermis in BIO172L.
Q3. Image/Specimen Identification Station 1: You are at a microscope station
examining a prepared slide. The instructor asks you to identify the numbered structure
indicated by the pointer. The structure is located at the top of the microscope body
tube, contains lenses, and is the lens you look through to view the specimen.
Identify the structure and state its standard magnification.
A. Objective lens; 40×
B. Ocular lens (eyepiece); 10×
C. Condenser lens; 20×
D. Iris diaphragm; 10×
Correct Answer: B
Rationale: [CORRECT] The ocular lens (eyepiece) is the lens at the top of the body tube
through which the viewer observes the specimen. In virtually all teaching compound
light microscopes used in BIO172L, the ocular lens has a fixed magnification of 10×.
Total magnification is calculated by multiplying ocular magnification (10×) by the
objective lens magnification (4×, 10×, 40×, or 100×).
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Q4. Calculation-Based A student examines a prepared slide of Paramecium using the
10× ocular and 4× scanning objective. The student then switches to the 40× high-power
objective. If the diameter of the field of view at 4× is 4.5 mm, what is the approximate
field of view diameter at 40×?
A. 45.0 mm
B. 0.45 mm
C. 4.5 mm
D. 0.045 mm
Correct Answer: B
Rationale: [CORRECT] Use the inverse proportional relationship: FOV~low~ ×
Mag~low~ = FOV~high~ × Mag~high~.
Step 1: Identify magnifications. Low power = 4×; high power = 40×.
Step 2: Set up the equation: 4.5 mm × 4 = FOV~high~ × 40.
Step 3: Solve for FOV~high~: (4.5 × 4) / 40 = = 0.45 mm.
This calculation confirms that increasing magnification tenfold reduces the field of view
diameter to one-tenth of its original size.
Q5. Multiple-Choice You are viewing a wet mount of Euglena and estimate that
approximately 15 organisms span the diameter of the field of view at 400× total
magnification. If the field of view at 400× is 0.45 mm, what is the approximate length of
one Euglena?
A. 0.03 mm
B. 0.30 mm
C. 3.0 mm
D. 30 mm
Correct Answer: A
Rationale: [CORRECT] To estimate specimen size, divide the field of view diameter by
the number of specimens that fit across it.
, 4
Step 1: FOV diameter = 0.45 mm.
Step 2: Number of specimens = 15.
Step 3: 0.45 mm ÷ 15 = 0.03 mm (or 30 µm).
This method is routinely used in BIO172L to estimate the size of microscopic organisms
when a stage micrometer is unavailable.
Q6. Multiple-Choice When preparing a wet mount of onion epidermis, you add a drop
of iodine solution to the specimen before placing the coverslip. What is the primary
purpose of this staining step?
A. To kill the cells and prevent movement
B. To increase the refractive index of the specimen
C. To enhance contrast by binding to starch and cellular structures
D. To fix the cells permanently to the slide
Correct Answer: C
Rationale: [CORRECT] Iodine acts as a contrast-enhancing stain in introductory biology
labs because it binds to starch granules and glycogen, producing a dark brown to black
coloration. This makes cellular structures—particularly nuclei and cell walls—visible
under brightfield microscopy. Iodine does not permanently fix cells (that requires
formaldehyde or alcohol-based fixatives) nor does it primarily prevent movement.
Q7. Select-All-That-Apply Which of the following statements correctly describe proper
wet mount preparation techniques used in BIO172L? Select all that apply.
A. Place the coverslip at a 45° angle and slowly lower it to minimize air bubbles
B. Apply excessive pressure to the coverslip to flatten the specimen completely
C. Use a dropper to place a small amount of water or staining solution on the slide
University of Hawaii at Hilo – BIO172L Lab
Practical Examination Instructor: Terre
Hawkins | Academic Year 2026/2027.
Domain 1: Microscopy & Laboratory Techniques.
Q1. Multiple-Choice When using the compound light microscope in the BIO172L lab,
you switch from the 10× objective to the 40× objective. Which of the following correctly
describes the change in working distance and field of view?
A. Working distance increases and field of view increases
B. Working distance decreases and field of view increases
C. Working distance decreases and field of view decreases
D. Working distance remains constant and field of view decreases
Correct Answer: C
Rationale: [CORRECT] As magnification increases from 10× to 40×, the working
distance (the space between the objective lens and the specimen) decreases, requiring
careful focus adjustment to avoid crushing the slide. Simultaneously, the field of view
decreases proportionally because higher magnification reveals a smaller area of the
specimen. This inverse relationship between magnification and field of view is
fundamental to microscope operation in introductory biology labs.
Q2. Multiple-Choice Which component of the compound light microscope is
responsible for concentrating and directing light onto the specimen?
A. The diaphragm
B. The condenser
, 2
C. The ocular lens
D. The coarse adjustment knob
Correct Answer: B
Rationale: [CORRECT] The condenser sits below the stage and gathers light from the
illuminator, focusing it into a cone of light that passes through the specimen. Proper
condenser adjustment (often paired with diaphragm regulation) is essential for
achieving maximal resolution and contrast when viewing wet mounts of Elodea or onion
epidermis in BIO172L.
Q3. Image/Specimen Identification Station 1: You are at a microscope station
examining a prepared slide. The instructor asks you to identify the numbered structure
indicated by the pointer. The structure is located at the top of the microscope body
tube, contains lenses, and is the lens you look through to view the specimen.
Identify the structure and state its standard magnification.
A. Objective lens; 40×
B. Ocular lens (eyepiece); 10×
C. Condenser lens; 20×
D. Iris diaphragm; 10×
Correct Answer: B
Rationale: [CORRECT] The ocular lens (eyepiece) is the lens at the top of the body tube
through which the viewer observes the specimen. In virtually all teaching compound
light microscopes used in BIO172L, the ocular lens has a fixed magnification of 10×.
Total magnification is calculated by multiplying ocular magnification (10×) by the
objective lens magnification (4×, 10×, 40×, or 100×).
, 3
Q4. Calculation-Based A student examines a prepared slide of Paramecium using the
10× ocular and 4× scanning objective. The student then switches to the 40× high-power
objective. If the diameter of the field of view at 4× is 4.5 mm, what is the approximate
field of view diameter at 40×?
A. 45.0 mm
B. 0.45 mm
C. 4.5 mm
D. 0.045 mm
Correct Answer: B
Rationale: [CORRECT] Use the inverse proportional relationship: FOV~low~ ×
Mag~low~ = FOV~high~ × Mag~high~.
Step 1: Identify magnifications. Low power = 4×; high power = 40×.
Step 2: Set up the equation: 4.5 mm × 4 = FOV~high~ × 40.
Step 3: Solve for FOV~high~: (4.5 × 4) / 40 = = 0.45 mm.
This calculation confirms that increasing magnification tenfold reduces the field of view
diameter to one-tenth of its original size.
Q5. Multiple-Choice You are viewing a wet mount of Euglena and estimate that
approximately 15 organisms span the diameter of the field of view at 400× total
magnification. If the field of view at 400× is 0.45 mm, what is the approximate length of
one Euglena?
A. 0.03 mm
B. 0.30 mm
C. 3.0 mm
D. 30 mm
Correct Answer: A
Rationale: [CORRECT] To estimate specimen size, divide the field of view diameter by
the number of specimens that fit across it.
, 4
Step 1: FOV diameter = 0.45 mm.
Step 2: Number of specimens = 15.
Step 3: 0.45 mm ÷ 15 = 0.03 mm (or 30 µm).
This method is routinely used in BIO172L to estimate the size of microscopic organisms
when a stage micrometer is unavailable.
Q6. Multiple-Choice When preparing a wet mount of onion epidermis, you add a drop
of iodine solution to the specimen before placing the coverslip. What is the primary
purpose of this staining step?
A. To kill the cells and prevent movement
B. To increase the refractive index of the specimen
C. To enhance contrast by binding to starch and cellular structures
D. To fix the cells permanently to the slide
Correct Answer: C
Rationale: [CORRECT] Iodine acts as a contrast-enhancing stain in introductory biology
labs because it binds to starch granules and glycogen, producing a dark brown to black
coloration. This makes cellular structures—particularly nuclei and cell walls—visible
under brightfield microscopy. Iodine does not permanently fix cells (that requires
formaldehyde or alcohol-based fixatives) nor does it primarily prevent movement.
Q7. Select-All-That-Apply Which of the following statements correctly describe proper
wet mount preparation techniques used in BIO172L? Select all that apply.
A. Place the coverslip at a 45° angle and slowly lower it to minimize air bubbles
B. Apply excessive pressure to the coverslip to flatten the specimen completely
C. Use a dropper to place a small amount of water or staining solution on the slide
