PORTAGE LEARNING
Bachelor of Science in Biology (BS)
BIOL 271 — Microbiology
Academic Year: 2026/2027
Module #3 Exam — Complete Question Bank
Portage Learning — Rigorous & Competency-Based
Question 1
Which type of microscopy uses electrons with specimens in a vacuum and has a
resolution of 1mm-0.1nm?
A. Light Microscopy
B. Electron Microscopy
C. Probe Microscopy
D. Phase Contrast Microscopy
CORRECT ANSWER B. Electron Microscopy
Rationale
Electron microscopy uses electrons with specimens in a vacuum, providing magnification of
1,000x-1,000,000x and resolution of 1mm-0.1nm. It is used to visualize prokaryotic cells,
viruses, macromolecules, and large atoms.
, Question 2
What is the function of the condenser in a brightfield microscope?
A. Magnifies the specimen
B. Focuses light through the specimen
C. Controls the amount of light entering
D. Transmits the image to the eye
CORRECT ANSWER B. Focuses light through the specimen
Rationale
In a brightfield microscope, before light reaches the sample, it first passes through the
condenser, which focuses the light through the specimen to improve resolution and
contrast.
Question 3
True or False: Longer wavelengths increase resolving power.
A. True
B. False
CORRECT ANSWER B. False
Rationale
Shorter wavelengths increase resolving power. The resolution of a microscope is inversely
proportional to the wavelength of light used — shorter wavelengths allow for better
resolution.
, Question 4
What is the function of the iris diaphragm in a brightfield microscope?
A. Magnifies the specimen
B. Focuses light through the specimen
C. Controls the amount of light entering the condenser
D. Supports the microscope
CORRECT ANSWER C. Controls the amount of light entering the condenser
Rationale
The iris diaphragm controls the amount of light entering the condenser. Adjusting the iris
diaphragm can improve contrast and resolution by regulating the light intensity.
Question 5
Which type of microscopy uses UV light to excite fluorophores and is used as a
diagnostic tool?
A. Phase Contrast Microscopy
B. Dark Field Microscopy
C. Fluorescence Microscopy
D. Bright Field Microscopy
CORRECT ANSWER C. Fluorescence Microscopy
Rationale
Fluorescence microscopy uses UV light to excite fluorophores, allowing visualization of
specific structures or molecules. It is commonly used as a diagnostic tool in clinical settings.
, Question 6
True or False: Most microorganisms are colorless, and staining increases contrast.
A. True
B. False
CORRECT ANSWER A. True
Rationale
Most microorganisms are colorless and transparent, making them difficult to observe
without staining. Staining increases contrast and allows visualization of cellular structures.
Question 7
What is the primary use of a wet mount in microbiology?
A. To stain the specimen
B. To observe motility and behavior of live organisms
C. To fix the specimen to the slide
D. To increase contrast
CORRECT ANSWER B. To observe motility and behavior of live organisms
Rationale
A wet mount is a basic preparation for viewing live samples. It allows observation of
motility and behavior of microorganisms without the need for staining or fixation.
Bachelor of Science in Biology (BS)
BIOL 271 — Microbiology
Academic Year: 2026/2027
Module #3 Exam — Complete Question Bank
Portage Learning — Rigorous & Competency-Based
Question 1
Which type of microscopy uses electrons with specimens in a vacuum and has a
resolution of 1mm-0.1nm?
A. Light Microscopy
B. Electron Microscopy
C. Probe Microscopy
D. Phase Contrast Microscopy
CORRECT ANSWER B. Electron Microscopy
Rationale
Electron microscopy uses electrons with specimens in a vacuum, providing magnification of
1,000x-1,000,000x and resolution of 1mm-0.1nm. It is used to visualize prokaryotic cells,
viruses, macromolecules, and large atoms.
, Question 2
What is the function of the condenser in a brightfield microscope?
A. Magnifies the specimen
B. Focuses light through the specimen
C. Controls the amount of light entering
D. Transmits the image to the eye
CORRECT ANSWER B. Focuses light through the specimen
Rationale
In a brightfield microscope, before light reaches the sample, it first passes through the
condenser, which focuses the light through the specimen to improve resolution and
contrast.
Question 3
True or False: Longer wavelengths increase resolving power.
A. True
B. False
CORRECT ANSWER B. False
Rationale
Shorter wavelengths increase resolving power. The resolution of a microscope is inversely
proportional to the wavelength of light used — shorter wavelengths allow for better
resolution.
, Question 4
What is the function of the iris diaphragm in a brightfield microscope?
A. Magnifies the specimen
B. Focuses light through the specimen
C. Controls the amount of light entering the condenser
D. Supports the microscope
CORRECT ANSWER C. Controls the amount of light entering the condenser
Rationale
The iris diaphragm controls the amount of light entering the condenser. Adjusting the iris
diaphragm can improve contrast and resolution by regulating the light intensity.
Question 5
Which type of microscopy uses UV light to excite fluorophores and is used as a
diagnostic tool?
A. Phase Contrast Microscopy
B. Dark Field Microscopy
C. Fluorescence Microscopy
D. Bright Field Microscopy
CORRECT ANSWER C. Fluorescence Microscopy
Rationale
Fluorescence microscopy uses UV light to excite fluorophores, allowing visualization of
specific structures or molecules. It is commonly used as a diagnostic tool in clinical settings.
, Question 6
True or False: Most microorganisms are colorless, and staining increases contrast.
A. True
B. False
CORRECT ANSWER A. True
Rationale
Most microorganisms are colorless and transparent, making them difficult to observe
without staining. Staining increases contrast and allows visualization of cellular structures.
Question 7
What is the primary use of a wet mount in microbiology?
A. To stain the specimen
B. To observe motility and behavior of live organisms
C. To fix the specimen to the slide
D. To increase contrast
CORRECT ANSWER B. To observe motility and behavior of live organisms
Rationale
A wet mount is a basic preparation for viewing live samples. It allows observation of
motility and behavior of microorganisms without the need for staining or fixation.
