Question 1

Which of the following best explains why scientists prefer to use metric units rather than English units in microbiology?

Accepted Answer

Metric units are easier to convert and are universally accepted in scientific research.

Question 2

A microbiologist is using a bright-field compound light microscope to observe bacteria. If the objective lens is 40x and the ocular lens is 10x, what is the total magnification?

Accepted Answer

$$40 	imes 10 = 400$$

Question 3

Which unit is most appropriate to measure the size of bacterial cells?

Accepted Answer

micrometer

Question 4

The ability of a microscope to distinguish two points that are close together is called:

Accepted Answer

resolution

Question 5

Which of the following forms of radiation has the shortest wavelength and therefore the highest resolving power in microscopy?

Accepted Answer

Gamma rays

Question 6

What is the effect of using immersion oil with a high-power objective lens?

Accepted Answer

It increases resolution by reducing light refraction.

Question 7

Which type of microscopy is best for observing live, colorless, or unstained cells?

Accepted Answer

Phase contrast microscopy

Question 8

A scientist wants to visualize the 3D surface structure of a virus. Which microscope should they use?

Accepted Answer

Scanning electron microscope (SEM)

Question 9

Which of the following statements about fluorescence microscopy is correct?

Accepted Answer

It uses UV light to excite fluorescent dyes, increasing resolution and contrast.

Question 10

The formula for resolution ($$r) in $$microscopy is $$r = 0.61 	imes \frac{\lambda}{NA}$$, where $$\lambda is $$the wavelength of light and $$NA is $$the numerical aperture. If you decrease $$\lambda$$ and increase $$NA$$, what happens to the resolution?

Accepted Answer

Resolution improves (smaller $$r$$ value)

Question 11

Which type of microscope would be most appropriate for visualizing the detailed internal structure of a bacterial cell at very high magnification?

Accepted Answer

Transmission electron microscope (TEM)

Question 12

What is the main advantage of using a confocal microscope over a traditional fluorescence microscope?

Accepted Answer

It constructs 3D images from digitized data, increasing resolution.

Question 13

Which of the following best describes the function of the numerical aperture (NA) in a microscope?

Accepted Answer

It determines the ability of the lens to gather light and resolve fine specimen detail.

Question 14

A sample is stained with a green fluorescent protein (GFP) and observed under a fluorescence microscope. What does the presence of green fluorescence indicate?

Accepted Answer

The cells express the protein tagged with GFP.

Question 15

Which of the following is a key difference between transmission electron microscopy (TEM) and scanning electron microscopy (SEM)?

Accepted Answer

TEM provides 2D images of internal structures, while SEM provides 3D images of surfaces.

Question 16

Which type of microscopy would be best for observing motility in live, unstained bacteria?

Accepted Answer

Dark-field microscopy

Question 17

Why does staining a specimen often improve its visibility under a microscope?

Accepted Answer

Staining increases contrast between the specimen and the background.

Question 18

Which of the following is the correct order of metric units from smallest to largest?

Accepted Answer

nanometer, micrometer, millimeter

Question 19

A researcher wants to study the atomic structure of a protein. Which type of microscopy should they use?

Accepted Answer

Probe microscopy (atomic force microscope)

Question 20

Which of the following best describes the principle of phase contrast microscopy?

Accepted Answer

It enhances contrast by amplifying differences in the refractive index of cell components.

Chp 4 Microscopy, Staining, and Classification: Study Notes for Microbiology

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