Q: What is the formula for total magnification in a compound light microscope?

$\text{Total Magnification} = \text{Objective Lens Magnification} \times \text{Ocular Lens Magnification}$

Question 1

Which of the following best describes the main advantage of using immersion oil with a light microscope?

Accepted Answer

It decreases the refractive index between the specimen and the lens, improving resolution.

Question 2

A microbiologist wants to observe the detailed surface structure of a virus particle. Which microscope should they use?

Accepted Answer

Scanning electron microscope (SEM)

Question 3

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

Accepted Answer

Ziehl-Neelsen acid-fast stain

Question 4

What is the main purpose of using a dichotomous taxonomic key in microbiology?

Accepted Answer

To systematically identify organisms based on a series of choices between alternative characteristics

Question 5

Which of the following is the correct order of steps in the Gram staining procedure?

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Question 6

A student observes a bacterial cell under a microscope and notes that it appears purple after Gram staining. What does this indicate about the cell wall structure?

Accepted Answer

The cell wall contains a thick layer of peptidoglycan.

Question 7

Which metric unit would be most appropriate for measuring the size of a typical bacterial cell?

Accepted Answer

Micrometer

Question 8

What is the formula for total magnification in a compound light microscope?

Accepted Answer

$	ext{Total Magnification} = 	ext{Objective Lens Magnification} 	imes 	ext{Ocular Lens Magnification}$

Question 9

Which property of light is most important for a microscope’s ability to distinguish two closely spaced objects as separate?

Accepted Answer

Resolution

Question 10

A clinical laboratory is testing for the presence of a bacterial capsule. Which staining technique should be used?

Accepted Answer

Negative stain

Question 11

Which of the following best explains why electron microscopes can resolve much smaller structures than light microscopes?

Accepted Answer

Electrons have a much shorter wavelength than visible light.

Question 12

Which of the following is a differential stain used to distinguish between types of bacteria based on cell wall composition?

Accepted Answer

Gram stain

Question 13

A scientist wants to visualize the location of a specific protein within a bacterial cell using a fluorescent dye. Which microscopy technique should they use?

Accepted Answer

Immunofluorescence microscopy

Question 14

Which of the following best describes the purpose of a phase-contrast microscope?

Accepted Answer

To visualize live, unstained cells by enhancing differences in refractive index

Question 15

Which of the following is the smallest unit of measurement?

Accepted Answer

Nanometer

Question 16

A microbiologist is using a dichotomous key to identify an unknown bacterium. Which of the following steps would most likely come first?

Accepted Answer

Determine if the bacterium is Gram-positive or Gram-negative

Question 17

Which of the following best describes the function of a serological test in microbiology?

Accepted Answer

To detect the presence of specific antigens or antibodies

Question 18

Which of the following is a reason why some bacteria, such as those of the genus Mycobacterium, do NOT effectively stain with the Gram stain?

Accepted Answer

They have a waxy cell wall rich in mycolic acids

Question 19

Which of the following best describes the difference between a simple stain and a differential stain?

Accepted Answer

A simple stain colors all cells the same, while a differential stain distinguishes between cell types or structures

Question 20

Which of the following is the correct formula for resolution ($d$) in microscopy?

Accepted Answer

$d = \frac{0.61 \lambda}{n \sin 	heta}$

Chpt 4 Lecture Microscopy, Staining, and Classification in Microbiology

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