Q: Which of the following equations correctly represents the calculation for total magnification in a compound light microscope?

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

Question 1

Which of the following best explains why oil immersion increases the resolution of a light microscope?

Accepted Answer

Oil reduces light refraction by matching the refractive index of glass, allowing more light to enter the objective lens.

Question 2

A microbiologist wants to observe living, unstained cells to study their internal structures. Which type of microscope should they use?

Accepted Answer

Phase-contrast microscope

Question 3

Which of the following equations correctly represents the calculation for total magnification in a compound light microscope?

Accepted Answer

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

Question 4

A clinical laboratory is using immunofluorescence to rapidly identify a bacterial pathogen in a patient sample. What is the primary advantage of this technique?

Accepted Answer

It increases resolution and contrast by using UV light and fluorescent dyes to specifically label target molecules.

Question 5

Which of the following statements about Gram staining is correct?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and retain the crystal violet stain.

Question 6

A scientist is using a scanning electron microscope (SEM) to study the surface of a virus. Which feature of SEM makes it suitable for this purpose?

Accepted Answer

SEM produces detailed three-dimensional images of specimen surfaces.

Question 7

Which of the following best describes the role of contrast in microscopy?

Accepted Answer

Contrast is the difference in intensity between an object and its background, which is often increased by staining.

Question 8

A hospital is using MALDI/TOF mass spectrometry to identify a bacterial pathogen. What is the principle behind this technique?

Accepted Answer

It sorts organic molecules by their mass-to-charge ratios to identify unique proteins synthesized by microbes.

Question 9

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

Accepted Answer

Acid-fast stain

Question 10

A researcher is using a dichotomous key to identify an unknown microorganism. What is the defining feature of a dichotomous key?

Accepted Answer

It uses a series of paired statements, each with two choices, to guide identification.

Question 11

Which of the following is a correct statement about the classification of organisms according to modern taxonomy?

Accepted Answer

Modern taxonomy aims to reflect phylogenetic relationships, often using genetic material comparisons.

Question 12

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

Accepted Answer

Most bacterial cells are negatively charged and attract basic dyes, which are cationic.

Question 13

A laboratory technician is using a phase-contrast microscope. What is the main advantage of this type of microscope?

Accepted Answer

It allows for the observation of living, unstained specimens by enhancing contrast through differences in phase.

Question 14

Which of the following is a unique feature of confocal microscopy compared to traditional fluorescence microscopy?

Accepted Answer

Confocal microscopy uses UV lasers and a pinhole aperture to increase resolution and construct 3D images.

Question 15

Which of the following is the correct order of taxonomic categories from most inclusive to least inclusive?

Accepted Answer

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Question 16

A sample is observed under a microscope and appears as light objects against a dark background. Which type of microscopy is being used?

Accepted Answer

Dark-field microscopy

Question 17

Which of the following best describes the principle of phage typing in bacterial identification?

Accepted Answer

It uses bacteriophages that are specific for certain bacterial hosts to identify bacteria based on susceptibility to infection.

Question 18

Which of the following is a limitation of light microscopes compared to electron microscopes?

Accepted Answer

Light microscopes cannot resolve structures closer than 200 nm due to the wavelength of visible light.

Question 19

A scientist is comparing the G + C content of two bacterial species' DNA. What is the purpose of this analysis?

Accepted Answer

To classify and identify microbes based on their nucleic acid composition.

Microscopy, Staining, and Classification in Microbiology

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