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

Total magnification is $$40 \times 10 = 400$$

Question 1

Which of the following best describes the principle of resolution in microscopy?

Accepted Answer

The ability of the lenses to distinguish two points as separate.

Question 2

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

Accepted Answer

Total magnification is $$40 	imes 10 = 400$$

Question 3

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

Accepted Answer

To prevent light from refracting and being lost, thus increasing resolution.

Question 4

Which type of microscopy would be most appropriate for visualizing viruses?

Accepted Answer

Transmission electron microscopy

Question 5

In fluorescence microscopy, what is the role of fluorochromes?

Accepted Answer

They absorb UV light and emit visible light.

Question 6

A patient specimen is tested using the fluorescent-antibody technique. What does a positive result indicate?

Accepted Answer

The specimen contains the pathogenic microbe, which fluoresces due to antibody binding.

Question 7

Which of the following statements about electron microscopy is correct?

Accepted Answer

Electron microscopes use electrons, which have shorter wavelengths than light, resulting in greater resolution.

Question 8

What is the main difference between transmission electron microscopy (TEM) and scanning electron microscopy (SEM)?

Accepted Answer

TEM passes electrons through thin sections to view internal structures, while SEM scans the surface for 3D images.

Question 9

Which dye would be most appropriate for negative staining of bacterial capsules?

Accepted Answer

India ink or nigrosin

Question 10

During Gram staining, what is the color of gram-negative bacteria after the decolorizing step?

Accepted Answer

Colorless

Question 11

Which of the following best explains why Gram stains are most consistent when used on young, actively growing bacteria?

Accepted Answer

Older bacteria may have damaged cell walls, affecting stain retention.

Question 12

Which staining technique is used to identify Mycobacterium tuberculosis in clinical specimens?

Accepted Answer

Acid-fast stain

Question 13

What is the primary stain used in the Schaeffer-Fulton endospore staining method?

Accepted Answer

Malachite green

Question 14

Which of the following is true regarding basic and acidic dyes?

Accepted Answer

Basic dyes have a cationic chromophore and adhere to negatively charged bacterial cells.

Question 15

A microbiologist wants to visualize the arrangement of flagella on a bacterial cell. Which staining method should be used?

Accepted Answer

Flagella stain with mordant and carbolfuchsin

Question 16

Which step in Gram staining is responsible for differentiating between gram-positive and gram-negative bacteria?

Accepted Answer

Decolorization with alcohol or acetone-alcohol

Question 17

A bacterial cell is stained red after acid-fast staining. What does this indicate?

Accepted Answer

The cell is acid-fast.

Question 18

Which of the following best describes the purpose of a mordant in staining procedures?

Accepted Answer

To increase the affinity of the stain for the specimen or to coat the specimen to enlarge it.

Question 19

Which microscopy technique would be most suitable for observing living, unstained microorganisms?

Accepted Answer

Phase-contrast microscopy

Question 20

A microbiologist observes green structures inside red bacterial cells after endospore staining. What is the interpretation?

Accepted Answer

The green structures are endospores, and the red cells are vegetative cells.

Microscopy and Staining Techniques in Microbiology

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