Q: Which of the following correctly describes the relationship between micrometers ($$\mum$$), nanometers (nm), and meters (m)?

$$1\ \mu\text{m} = 10$$^{-6}$$\ \text{m}$$ and $$1\ \text{nm} = 10$$^{-9}$$\ \text{m}$$

Q: A microscope has a resolving power of $$0.2\ \mu\text{m}. $$What does this mean?

It can distinguish two points at least $$0.2\ \mu\text{m}$$ apart

Question 1

Which of the following correctly describes the relationship between micrometers ($$\mum$$), nanometers (nm), and meters (m)?

Accepted Answer

$$1\ \mu	ext{m} = 10$$^{-6}$$\ 	ext{m}$$ and $$1\ 	ext{nm} = 10$$^{-9}$$\ 	ext{m}$$

Question 2

A compound light microscope has an objective lens of 40x and an ocular lens of 10x. What is the total magnification?

Accepted Answer

$$400	imes$$

Question 3

Which microscopy technique would be most appropriate for observing live, unstained spirochetes such as Treponema pallidum?

Accepted Answer

Darkfield microscopy

Question 4

Why is immersion oil used with the oil immersion objective lens in light microscopy?

Accepted Answer

To reduce light refraction and increase resolution

Question 5

A microscope has a resolving power of $$0.2\ \mu	ext{m}. $$What does this mean?

Accepted Answer

It can distinguish two points at least $$0.2\ \mu	ext{m}$$ apart

Question 6

Which of the following stains would be most appropriate for identifying Mycobacterium tuberculosis in a clinical sample?

Accepted Answer

Acid-fast stain

Question 7

What is the primary difference between Gram-positive and Gram-negative bacteria as revealed by the Gram stain?

Accepted Answer

Gram-positive bacteria have thick peptidoglycan walls and stain purple; Gram-negative have thin walls and stain pink/red

Question 8

Which microscopy technique would be best for visualizing the three-dimensional surface structure of a bacterial cell?

Accepted Answer

Scanning electron microscopy (SEM)

Question 9

Why do electron microscopes have greater resolution than light microscopes?

Accepted Answer

Electrons have shorter wavelengths than visible light

Question 10

Which of the following best describes the principle of fluorescence microscopy?

Accepted Answer

Fluorescent substances absorb UV light and emit visible light

Question 11

A clinical laboratory wants to rapidly and specifically detect a pathogenic bacterium in a patient sample. Which technique should they use?

Accepted Answer

Immunofluorescence (fluorescent-antibody technique)

Question 12

Which of the following is a correct sequence of steps in the Gram stain procedure?

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Question 13

Which type of dye is most likely to stain bacterial cells directly, and why?

Accepted Answer

Basic dye, because bacterial cells are negatively charged

Question 14

Which microscopy technique allows for the mapping of atomic and molecular shapes without modifying the specimen?

Accepted Answer

Scanned-probe microscopy

Question 15

A scientist wants to observe the internal structure of a thin slice of a eukaryotic cell at very high resolution. Which instrument should they use?

Accepted Answer

Transmission electron microscope (TEM)

Question 16

Which of the following best explains why negative stains do not color bacterial cells?

Accepted Answer

Acidic dyes are repelled by the negatively charged bacterial cell surface

Question 17

Which special stain would you use to visualize the presence and arrangement of bacterial flagella?

Accepted Answer

Flagella stain with a mordant and carbolfuchsin

Question 18

Which of the following is a key advantage of confocal microscopy over traditional fluorescence microscopy?

Accepted Answer

It produces clear two-dimensional images of a single plane and can reconstruct three-dimensional images

Question 19

A sample contains both endospores and vegetative cells. After performing the Schaeffer-Fulton endospore stain, what colors would you expect to see under the microscope?

Accepted Answer

Endospores appear green, vegetative cells appear red or pink

Question 20

Which microscopy technique would be most suitable for studying the activity of living cells up to 1 millimeter deep in real time?

Accepted Answer

Two-photon microscopy

Observing Microorganisms Through a Microscope: Principles and Techniques

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