Deck 3: Microscopy and Staining

Question 1

Which of the following statements about Leeuwenhoek's microscopes is false?

A) Leeuwenhoek kept his technique secret
B) they magnified objects 100 to 300 times
C) for each specimen a new microscope had to be made
D) they were able to reveal very fine details of bacteria

Answer 1

D

Question 2

The total magnification of a specimen being viewed with a 10X ocular lens and a 40X objective lens is

A) 4X
B) 40X
C) 400X
D) 4000X

Answer 2

C

Question 3

Diffraction occurs when

A) light is reflected by an object
B) light passes through a small opening
C) light changes wavelengths
D) light is absorbed by a normally transparent object (like a glass slide)

Answer 3

B

Question 4

A compound microscope

A) has two eyepieces
B) has a total magnification of 5,000X
C) has only fine adjustment and no coarse adjustment
D) has more than one lens

Question 5

The lens closest to your eyes during a microscopic examination is the

A) ocular
B) objective
C) condenser
D) compound

Question 6

When light rays pass into an object but do not emerge,________ has taken place.

A) reflection
B) absorption
C) refraction
D) transmission

Question 7

A compound light microscope can generally see objects no smaller than

A) a ribosome
B) a large protozoa
C) a small bacterium
D) a typical virus

Question 8

Electron microscopes have a much better resolving power when compared to light microscopes because

A) electrons are invisible to the eye
B) electrons have longer wavelengths than visible light rays
C) electrons have shorter wavelengths than visible light rays
D) electrons are negatively charged

Question 9

When light passes through an object,________ of the light has occurred.

A) reflection
B) absorption
C) transmission
D) fluorescence

Question 10

Which of the following statements about resolution is true?

A) refers to the ability of a lens to distinguish adjacent objects
B) with regard to light, means the same thing as wavelength
C) refers to a microscope's ability to magnify objects
D) is equal to the distance between two adjacent crests of a wave

Question 11

During microscopic observation of a specimen,the amount of light that is allowed to pass through the specimen is controlled by the

A) condenser
B) objective lens
C) iris diaphragm
D) ocular lens

Question 12

In order to make use of light for a microscopic examination of an object the object must ________ or ________ light.

A) absorb, luminesce
B) transmit, absorb
C) transmit, reflect
D) reflect, absorb

Question 13

The lens closest to the slide during a microscopic examination is the

A) ocular
B) objective
C) condenser
D) compound

Question 14

Most light microscopes contain a/n ________ that converges the light beam so that it passes through the specimen

A) objective lens
B) iris diaphragm
C) mechanical stage
D) condenser

Question 15

When light bends as it passes through an object,________ of the light has occurred.

A) reflection
B) absorption
C) transmission
D) refraction

Question 16

The formula for resolving power of a lens is l/2NA (wavelength /2 x numerical aperture). What does this say about resolving power?

A) the smaller the wavelength the greater the resolving power of the lens
B) it is not related to the lens' numerical aperture
C) we can not precisely calculate the resolving power of a lens
D) a larger resolving power is indicative of a better lens

Question 17

What is true about the index of refraction?

A) if light rays are taken up by the object then it has a high index of refraction
B) it measures the frequency of the light as it reflects from a material
C) oil immersion lenses increase the problem of refraction
D) light will bend as it passes through two substances with different indices of refraction

Question 18

Why is diffraction a problem for microscopy?

A) because the lens acts as a large aperture through which light must pass
B) the small size of higher-power lenses causes severe diffraction
C) loss of light results in blurred images
D) diffraction of light is useful when using an oil immersion lens to view objects

Question 19

Light of ________ wavelength typically will result in ________ resolution.

A) longer, better
B) shorter, better
C) any, poor
D) shorter, worse

Question 20

To calculate the total magnification of a light microscope you must know

A) the magnification of the objective and condenser lenses
B) the magnification of the ocular and condenser lenses
C) the magnification of objective, ocular and condenser lenses
D) the magnification of the objective and ocular lenses

Question 21

A parfocal microscope

A) has more than one source of illumination
B) has both coarse and fine focusing adjustment
C) accentuates small differences in the refractive index of intracellular structures
D) allows for specimens to remain in focus when changing between magnification

Question 22

The advent of the electron microscope allowed ________ to be viewed for the first time.

A) protozoa
B) bacteria
C) viruses
D) algae

Question 23

Electron microscopes use ________ to focus the electron beam.

A) glass lenses
B) electromagnets
C) mechanical stages
D) laser beams

Question 24

Ultraviolet light is a key component of

A) bright-field microscopy
B) dark-field microscopy
C) phase-contrast microscopy
D) fluorescence microscopy

Question 25

The term "basic dyes" refers to the fact that these dyes

A) are easily prepared
B) are positively charged
C) are attracted to positively charged cell structures
D) are simple in their composition

Question 26

Electron microscopes

A) that are scanning have better resolution than those that are transmission
B) are much more expensive and take up more space than light microscopes
C) can use the same preparations of specimens that have been prepared for viewing with a light microscope
D) have a resolving power approximately 10 times better than the best light microscope

Question 27

Which of the following is not a differential stain?

A) Gram stain
B) Schaeffer-Fulton
C) acid-fast stain
D) flagellar stain

Question 28

Transmission electron microscopes have a maximum magnification of

A) 1,000X
B) 100,000X
C) 500,000X
D) 1,000,000X

Question 29

Which of the following statements about preparing a specimen is false?

A) organisms must be heat fixed before viewed in a hanging drop slide
B) smears are loopful of medium spread on the surface of a glass slide
C) wet mount preparations give good views of microbial mobility
D) the depth of a smear affects the results as too thin you may find no organisms

Question 30

Three dimensional views of cells and other small objects could best be obtained using a

A) phase contrast microscope
B) dark-field microscope
C) transmission electron microscope
D) scanning electron microscope

Question 31

The technique that involves the evaporation of water from a frozen and fractured specimen is called

A) shadow casting
B) freeze-etching
C) heat fixation
D) freeze-fracturing

Question 32

Atomic force microscope

A) allows 3 dimensional imaging and measurement of structures as small as nucleotides in DNA
B) is not yet capable of measuring small forces
C) involves ultraviolet light exciting molecules so that they release light of a longer wavelength
D) has a special condenser and objective lens

Question 33

Which of the following can be used to examine live specimens?

A) transmission electron microscope
B) scanning electron microscope
C) scanning tunneling electron microscope
D) atomic force microscope

Question 34

The best electron microscopes have a resolution of

A) 0.1 nm
B) 1 nm
C) 10 nm
D) 100 nm

Question 35

In a Gram stain,the mordant is

A) crystal violet
B) iodine
C) water
D) alcohol

Question 36

Colored photos of electron micrographs

A) reflect the color of the specimen before it was frozen
B) are false color added on during image preparation
C) reflect the color of the specimen after it was frozen
D) are always in pastel shades

Question 37

A simple stain

A) uses only a single dye
B) requires only one step to stain a slide
C) distinguishes between two different parts of an organism
D) is composed of an equal balance of acid and basic dyes

Question 38

Which is a false statement about light microscopy?

A) a dark-field microscope produces bright images against a dark background
B) a phase contrast microscope gives 3 dimensional images
C) fluorescent antibody staining can not determine whether a foreign substance such as a microbe is present in a specimen
D) a Nomarski microscope produces much higher resolution than the standard phase-contrasting microscope

Question 39

A microscope that converts changes in the speed of light as it passes through an object into differences in brightness is a ________ microscope.

A) bright field
B) dark field
C) phase-contrast
D) Nomarski

Question 40

A microscope in which light rays pass directly through a specimen is a ________ microscope.

A) bright field
B) dark field
C) phase-contrast
D) Nomarski

Question 41

Bacteria capsules can best be visualized by _______ staining.

A) flagellar
B) crystal violet
C) negative
D) mordant

Question 42

The counterstain in a spore stain is

A) malachite green
B) crystal violet
C) safranin
D) methylene blue

Question 43

Compare and contrast light microscopy to electron microscopy. Be sure to include how they work and what they can see (or the extent of their total magnification).

Question 44

Why do basic dyes attach to most bacterial surfaces?

A) most bactieral surfaces are negatively charged
B) because cells take up safranin
C) most bacterial surfaces resist taking up the stain
D) most bacterial surfaces do not have a charge

Question 45

Which type of staining results in a clear object being viewed against a dark background

A) simple stain
B) negative stain
C) endospore stain
D) flagellar stain

Question 46

Which stain would be the best choice for detecting mycobacterium (the bacteria responsible for tuberculosis and leprosy)?

A) simple stain
B) endospore stain
C) acid-fast stain
D) Gram stain

Question 47

In a properly executed Gram stain,Gram positive organisms appear ________ while Gram negative organisms appear ________.

A) pink, clear
B) pink, purple
C) purple, pink
D) purple, blue

Question 48

What statement about microscopy and staining techniques is false?

A) many species look identical under the microscope
B) staining and microscopic examination are usually all that is need to identify a microorganism.
C) microscopes are of little use unless the specimens are prepared properly
D) degree of contrast is equally important as resolution and magnification

Question 49

When given a microorganism to identify,which of the following would be useful?

A) a gram stain
B) a transmission electron micrograph
C) biochemical and genetic characteristics
D) all of the above

Question 50

Would light of a higher or lower wavelength give you better resolution when using a microscope? Why? Would a light microscope that had a total magnification of 500X give you better resolution than one that has a magnification of 100X? Why?

Question 51

If the step involving iodine were left out of a Gram stain,which of the following would best describe the results?

A) Gram negative cells would look Gram positive
B) Gram positive cells would look Gram negative
C) All rods would be pink, all cocci purple
D) All cells would be purple

Question 52

The stains used in the Ziehl-Neelsen acid-fast stain are

A) crystal violet and eosin
B) carbolfuschin and methylene blue
C) carbolfuschin and safranin
D) safranin and methylene blue

Question 53

What is the Wright stain? What does it distinguish?