Micro Chapter 2 Flashcards
The degree to which a substance bends light is known as the A) Resolution B) Numerical aperture C) Refractive index D) Magnification
C
When light passes from air to a medium with a great refractive index (i.e., glass), what happens to the light?
A) The velocity of light decreases and it bends away from the normal
B) The velocity of light decreases and it bends toward the normal
C) The velocity of light increases and it bends away from the normal
D) The velocity of light increases and it bends toward the normal
B
Which of the following best describes how a lens works?
A) Light rays strike the lens and scatter
B) Light rays strike the lens and converge onto a focal point
C) Light rays move through the lens without changing direction
D) None of the above
B
A microscope that can remain in focus when the objective lens is changed is described as A) Refractive B) Magnified C) Parfocal D) All of the above
C
The total magnification of a bright-field microscope with a 10X eyepiece on the high power (100X) objective would be A) 100X B) 110X C) 1000X D) 10,000X
C
The ability of a lens to separate or distinguish between small objects that are close together is called A) Magnification B) Numerical aperture C) Refractive index D) Resolution
D
Which of the following changes would increase the resolution of a specimen observed through a lens? A) Decrease the wavelength of light B) Increase the refractive index C) Increase the numerical aperture D) All of the above
D
Immersion oil is used when observing specimens under high power because
A) It decreases the refractive index; this increases the numerical aperture
B) It increases the refractive index; this decreases the numerical aperture
C) It decreases the refractive index; this decreases the numerical aperture
D) It increases the refractive index; this increases the numerical aperture
A
The distance between the front surface of the lens and the surface of the cover glass or specimen is called the A) Numerical aperture B) Focal length C) Working distance D) Resolution
C
The best resolution achieved by bright-field microscopes is approximately A) 10 micrometers B) 1 micrometer C) 0.2 micrometers D) 0.2 nanometers
C
A bright-field microscope is best for observing which of the following types of specimens? A) Fixed, stained bacteria B) Unpigmented living cells C) Viruses D) Atoms
A
A dark-field microscope is best for observing which of the following types of specimens? A) Fixed, stained bacteria B) Unpigmented living cells C) Viruses D) Atoms
B
Which of the following microscopes are acceptable for viewing live specimens?
A) Dark-field microscope
B) Phase-contrast microscope
C) Differential interference contrast microscope
D) All of the above
D
The \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ microscope utilizes differences in refractive index and cell density into detectable variations in light intensity. A) Bright-field B) Dark-field C) Phase-contrast D) Electron
C
Which type of microscope would be best for observing microbial motility and observing endospores? A) Bright-field B) Dark-field C) Phase-contrast D) Electron
C
The ____________________ microscope allows microbiologists to view three-dimensional live specimens in bright color.
A) Differential interference contrast (DIC)
B) Dark-field
C) Bright-field
D) Phase-contrast
A
Fluorescence microscopy takes advantage of which of the following characteristics of objects and light?
A) Molecules of objects reflect radiant energy and release this trapped energy as light
B) Molecules of objects absorb radiant energy and release this trapped energy as light
C) Molecules of objects reflect radiant energy and absorb this trapped energy as light
D) Molecules of objects absorb radiant energy and absorb this trapped energy as light
B
Which type of microscopy exposes a specimen to low wavelength light and forms an image of the object with resulting fluorescent light?
A) Phase-contrast microscopy
B) Differential interference contrast (DIC) microscopy
C) Electron microscopy
D) Fluorescence microscopy
D
Fluorescence microscopy is most useful in which of the following?
A) Observing bacteria tagged with fluorescently labeled antibodies
B) Visualizing organisms that fluorescence naturally
C) Observing the localization of specific proteins within the cell
D) All of the above
D
The best type of microscopy for observing layered specimens (i.e., biofilms on medical devices) is
A) Phase-contrast microscopy
B) Differential interference contrast (DIC) microscopy
C) Confocal microscopy
D) Electron microscopy
C
Fixing cells is advantageous in that it
A) Kills cells
B) Toughens cell structures so that they remain during staining
C) Allows for observation of metabolic processes
D) All of the above
B
Basic dyes work by
A) Binding to negatively charged molecules on the surface of cells
B) Binding to positively charged molecules on the surface of cells
C) Bind with cells by hydrophobic interactions
D) None of the above
A
Failure to complete the decolorization step in the Gram stain will result in
A) All cells appearing clear or unstained
B) All cells will appear purple, or stained with crystal violet
C) All cells will appear pink, or stained with safranin
D) No change; Gram positive cells will appear purple and Gram positive cells will appear pink
B
Iodine, the mordant in the Gram staining procedure, is used to
A) Help bind the crystal violet to the target molecule
B) Help decolorize the crystal violet from Gram-positive cells
C) Help bind the safranin to the target molecule
D) None of the above
A
