Q: Which of the following is the correct metric conversion for 0.5 millimeters (mm) to micrometers (µm)?

$$0.5 \text{ mm} \times 1000 = 500$$ \mu m

Question 1

A bacterium is measured to be 2 µm in length. How many nanometers (nm) is this bacterium?

Accepted Answer

$$2 	imes 10^3$ nm

Question 2

Which microscope would you use to observe the internal structure of a mitochondrion, and what type of image would you expect?

Accepted Answer

Transmission Electron Microscope (TEM); 2D image

Question 3

A student observes a specimen using a 40× objective lens and a 10× ocular lens. What is the total magnification?

Accepted Answer

$$400	imes$$

Question 4

Which staining method would you use to distinguish between Mycobacterium tuberculosis and Escherichia coli, and what would be the expected result for each?

Accepted Answer

Acid-fast stain; Mycobacterium tuberculosis = red/pink, Escherichia coli = blue

Question 5

Which of the following best describes the function of the condenser in a compound light microscope?

Accepted Answer

Directs and focuses light through the specimen

Question 6

A clinical sample is stained and observed under a microscope. The cells appear pink after Gram staining. What can you infer about the cell wall structure?

Accepted Answer

Thin peptidoglycan layer and an outer membrane

Question 7

Which of the following bacteria is NOT an endospore producer?

Accepted Answer

Mycobacterium tuberculosis

Question 8

You are asked to prepare a slide to observe live, unstained spirochetes. Which microscopy technique should you use?

Accepted Answer

Darkfield microscopy

Question 9

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

Accepted Answer

Crystal violet → Iodine → Alcohol → Safranin

Question 10

A virus is measured to be 120 nm in diameter. What is its size in micrometers (µm)?

Accepted Answer

$$0.12$$ \mu m

Question 11

Which microscope would be most appropriate for viewing the surface details of a bacterial flagellum?

Accepted Answer

Scanning Electron Microscope (SEM)

Question 12

Which of the following statements about resolution is TRUE?

Accepted Answer

Shorter wavelength of light results in better resolution

Question 13

Which stain would you use to visualize the background rather than the bacterial cell, and what is the charge of the dye used?

Accepted Answer

Acidic stain; negatively charged dye

Question 14

A sample contains both Bacillus and Clostridium species. What do these genera have in common?

Accepted Answer

Both are Gram-positive rods that produce endospores

Question 15

Which microscope component is responsible for remagnifying the image formed by the objective lens?

Accepted Answer

Ocular lens (eyepiece)

Question 16

A student wants to observe the internal organelles of a eukaryotic cell in three dimensions. Which microscope should they use?

Accepted Answer

Confocal microscope

Question 17

Which of the following is a differential stain?

Accepted Answer

Gram stain

Question 18

A sample is stained with carbolfuchsin, heated, treated with acid alcohol, and counterstained with methylene blue. What type of bacteria will appear red/pink?

Accepted Answer

Acid-fast bacteria

Question 19

Which of the following is the correct metric conversion for 0.5 millimeters (mm) to micrometers (µm)?

Accepted Answer

$$0.5 	ext{ mm} 	imes 1000 = 500$$ \mu m

Question 20

Which of the following best explains why immersion oil is used with the 100× objective lens?

Accepted Answer

It reduces light refraction and improves resolution

Observing Microorganisms Through a Microscope: Study Guide and Metric Conversions

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