Question 1

Which of the following best describes the difference between magnification and resolution in microscopy?

Accepted Answer

Magnification is the degree to which the image of a specimen is enlarged, while resolution is the ability to distinguish two points as separate.

Question 2

A microbiologist is using a compound light microscope with a 40X objective lens and a 10X ocular lens. What is the total magnification?

Accepted Answer

$$40 	imes 10 = 400$$

Question 3

Which of the following units is the smallest?

Accepted Answer

1 nanometer ($$1\ \mathrm{nm})$$

Question 4

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

Accepted Answer

It reduces the bending of light (refraction) and increases resolution.

Question 5

A scientist wants to observe the detailed surface structure of a virus particle. Which type of microscopy should they use and why?

Accepted Answer

Scanning electron microscopy, because it scans the surface and provides high-resolution 3D images.

Question 6

Which of the following statements about the Gram stain is correct?

Accepted Answer

Gram-positive bacteria are more susceptible to penicillin and detergents.

Question 7

A microbiologist prepares a smear and uses a basic dye for staining. What is the charge of the chromophore in the dye, and what does it stain?

Accepted Answer

The chromophore is a cation and stains the cell.

Question 8

Which of the following best explains why electron microscopes have greater resolving power than light microscopes?

Accepted Answer

Electrons have a shorter wavelength than visible light.

Question 9

A sample is stained with malachite green and safranin. Under the microscope, some cells appear green and others red. What structure is being identified?

Accepted Answer

Endospores

Question 10

Which of the following is a correct conversion?

Accepted Answer

$$1\ \mathrm{\mu m} = 10$$^{-6}$$\ \mathrm{m}$$

Question 11

A clinical lab receives a sputum sample suspected of containing Mycobacterium tuberculosis. Which staining technique should be used and why?

Accepted Answer

Acid-fast stain, because Mycobacterium has a waxy cell wall that resists decolorization.

Question 12

Which of the following best describes negative staining?

Accepted Answer

An acidic dye stains the background, leaving the cell colorless.

Question 13

A microbiologist wants to observe living, unstained cells to study their behavior. Which type of microscopy is most appropriate?

Accepted Answer

Phase-contrast microscopy

Question 14

Which of the following is NOT a type of light microscopy?

Accepted Answer

Scanning electron microscopy

Question 15

A specimen is observed under a microscope and appears colorless after the decolorizing step of the Gram stain. What is the most likely type of bacteria?

Accepted Answer

Gram-negative

Question 16

Which of the following best explains why a mordant is used in staining procedures?

Accepted Answer

To hold the stain or coat the specimen to enlarge it

Question 17

A microbiologist is using a simple microscope. Which of the following is true about this instrument?

Accepted Answer

It has only one lens.

Question 18

Which of the following is a correct statement about the preparation of smears for staining?

Accepted Answer

The smear is usually fixed to attach the microbes to the slide and to kill the microbes.

Question 19

Which of the following stains is specifically used to visualize the gelatinous coating surrounding some bacteria?

Accepted Answer

Capsule stain

Question 20

A microbiologist is trying to identify bacteria based on the number and arrangement of flagella. Which staining technique should be used?

Accepted Answer

Flagella stain

Observing Microorganisms Through a Microscope: Principles and Techniques

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