,BIOD171/BIOD 171 Module 3 Exam | Essential Microbiology
with Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. A nanometer is defined as which of the following?
A) 10⁻³ meters
B) 10⁻⁶ meters
C) 10⁻⁹ meters
D) 10⁻¹² meters
Correct Answer: 10⁻⁹ meters
Rationale: A nanometer is one-billionth of a meter, which is written as 10⁻⁹ meters. A micrometer is 10⁻⁶
meters. This distinction is fundamental for understanding the scale of microorganisms.
2. True or False: A nanometer is longer than a micrometer.
A) True
B) False
Correct Answer: False
Rationale: A nanometer is 1,000 times smaller than a micrometer. Because a micrometer (10⁻⁶ m) is
larger than a nanometer (10⁻⁹ m), the statement is false.
3. Which of the following is the correct definition of a micrometer?
A) 10⁻³ meters
B) 10⁻⁶ meters
C) 10⁻⁹ meters
D) 10⁻¹² meters
Correct Answer: 10⁻⁶ meters
,Rationale: A micrometer is one-millionth of a meter. This is the standard unit for measuring most
bacteria and eukaryotic cells.
4. Resolution and contrast are two critical factors that influence your ability to see an object. What is the
correct definition of resolution?
A) The difference in light absorbance between two objects
B) The distance between two objects at which they can still be seen as separate
C) The total magnification of the microscope
D) The brightness of the light source
Correct Answer: The distance between two objects at which they can still be seen as separate
Rationale: Resolution is the ability to distinguish two points as separate entities. Poor resolution causes
objects to appear merged, while good resolution reveals fine structural details.
5. Which of the following best defines contrast in microscopy?
A) The distance between two objects at which they can still be seen as separate
B) The ability of the microscope to magnify an object
C) The difference in light absorbance between two objects
D) The wavelength of light used to illuminate the sample
Correct Answer: The difference in light absorbance between two objects
Rationale: Contrast is the difference in light intensity between the specimen and the background. Poor
contrast makes visualization difficult, while high contrast enhances the ability to see details.
6. Assuming a constant (non-adjustable) light source power, which part of the microscope would you
adjust to limit the amount of light entering the microscope?
A) Objective
, B) Condenser
C) Iris diaphragm
D) Eye piece
Correct Answer: Iris diaphragm
Rationale: The iris diaphragm controls the amount of light that passes through the sample and into the
objective lens. It can be opened or closed to adjust the light intensity.
7. What is the total magnification of a sample imaged with a 60x objective and a 10x eyepiece?
A) 60x
B) 70x
C) 600x
D) 6000x
Correct Answer: 600x
Rationale: Total magnification is calculated by multiplying the objective lens power by the ocular
(eyepiece) power. 60x × 10x = 600x magnification.
8. What is the total magnification of a sample imaged with a 20x objective and a 15x eyepiece?
A) 35x
B) 200x
C) 300x
D) 1500x
Correct Answer: 300x
Rationale: The total magnification is calculated by multiplying the objective magnification by the ocular
magnification. 20x × 15x = 300x magnification.
with Lab | Portage Learning | Q & A | 2026/2027 Edition (PDF)
1. A nanometer is defined as which of the following?
A) 10⁻³ meters
B) 10⁻⁶ meters
C) 10⁻⁹ meters
D) 10⁻¹² meters
Correct Answer: 10⁻⁹ meters
Rationale: A nanometer is one-billionth of a meter, which is written as 10⁻⁹ meters. A micrometer is 10⁻⁶
meters. This distinction is fundamental for understanding the scale of microorganisms.
2. True or False: A nanometer is longer than a micrometer.
A) True
B) False
Correct Answer: False
Rationale: A nanometer is 1,000 times smaller than a micrometer. Because a micrometer (10⁻⁶ m) is
larger than a nanometer (10⁻⁹ m), the statement is false.
3. Which of the following is the correct definition of a micrometer?
A) 10⁻³ meters
B) 10⁻⁶ meters
C) 10⁻⁹ meters
D) 10⁻¹² meters
Correct Answer: 10⁻⁶ meters
,Rationale: A micrometer is one-millionth of a meter. This is the standard unit for measuring most
bacteria and eukaryotic cells.
4. Resolution and contrast are two critical factors that influence your ability to see an object. What is the
correct definition of resolution?
A) The difference in light absorbance between two objects
B) The distance between two objects at which they can still be seen as separate
C) The total magnification of the microscope
D) The brightness of the light source
Correct Answer: The distance between two objects at which they can still be seen as separate
Rationale: Resolution is the ability to distinguish two points as separate entities. Poor resolution causes
objects to appear merged, while good resolution reveals fine structural details.
5. Which of the following best defines contrast in microscopy?
A) The distance between two objects at which they can still be seen as separate
B) The ability of the microscope to magnify an object
C) The difference in light absorbance between two objects
D) The wavelength of light used to illuminate the sample
Correct Answer: The difference in light absorbance between two objects
Rationale: Contrast is the difference in light intensity between the specimen and the background. Poor
contrast makes visualization difficult, while high contrast enhances the ability to see details.
6. Assuming a constant (non-adjustable) light source power, which part of the microscope would you
adjust to limit the amount of light entering the microscope?
A) Objective
, B) Condenser
C) Iris diaphragm
D) Eye piece
Correct Answer: Iris diaphragm
Rationale: The iris diaphragm controls the amount of light that passes through the sample and into the
objective lens. It can be opened or closed to adjust the light intensity.
7. What is the total magnification of a sample imaged with a 60x objective and a 10x eyepiece?
A) 60x
B) 70x
C) 600x
D) 6000x
Correct Answer: 600x
Rationale: Total magnification is calculated by multiplying the objective lens power by the ocular
(eyepiece) power. 60x × 10x = 600x magnification.
8. What is the total magnification of a sample imaged with a 20x objective and a 15x eyepiece?
A) 35x
B) 200x
C) 300x
D) 1500x
Correct Answer: 300x
Rationale: The total magnification is calculated by multiplying the objective magnification by the ocular
magnification. 20x × 15x = 300x magnification.
