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 an object 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 being used?

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

To reduce the bending of light and increase resolution by matching the refractive index of glass.

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 detailed 3D images.

Question 6

Which of the following statements about Gram staining is correct?

Accepted Answer

Gram-positive bacteria tend to be killed by penicillin and detergents.

Question 7

A microbiologist observes two points under a microscope that are 0.3 nm apart, but they appear as one. If the resolving power of the microscope is 0.4 nm, what does this indicate?

Accepted Answer

The microscope cannot resolve the two points as separate because they are closer than its resolving power.

Question 8

Which of the following stains would be most appropriate to visualize a bacterial capsule?

Accepted Answer

Negative stain

Question 9

What is the main advantage of using electron microscopy over light microscopy?

Accepted Answer

Electron microscopy provides greater resolution due to the shorter wavelength of electrons.

Question 10

Which of the following best explains why basic dyes are commonly used to stain bacterial cells?

Accepted Answer

Bacterial cell walls are negatively charged and attract the positively charged chromophore of basic dyes.

Question 11

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 12

Which of the following is a correct conversion?

Accepted Answer

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

Question 13

Which type of microscopy would be most suitable for observing living, unstained cells to study their behavior?

Accepted Answer

Phase-contrast microscopy

Question 14

A microbiologist is preparing a smear for staining. What is the primary purpose of fixing the smear?

Accepted Answer

To attach the microbes to the slide and kill them.

Question 15

Which of the following best describes the principle behind differential stains?

Accepted Answer

They distinguish between different types of bacteria based on their structural or chemical properties.

Question 16

A patient sample is stained using the acid-fast technique. The cells retain the primary stain after decolorization with acid-alcohol. What does this indicate?

Accepted Answer

The cells have a waxy cell wall characteristic of Mycobacterium species.

Question 17

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

Accepted Answer

Scanning electron microscopy

Question 18

Why are mordants sometimes used in staining procedures?

Accepted Answer

To hold the stain or coat the specimen to enlarge it.

Question 19

Which of the following best explains why Gram-negative bacteria are more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

They possess an outer lipopolysaccharide layer that acts as a barrier.

Question 20

A microbiologist wants to determine the number and arrangement of flagella on a bacterial cell. Which staining technique should be used?

Accepted Answer

Flagella stain with a mordant

Observing Microorganisms Through a Microscope: Principles and Techniques

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