Microbiology LAB Exam #1- Questions &
Answers
Microscope- The Condenser Correct Ans-focuses the light ging into the objective lens
Microscope- The Iris Diaphragm Correct Ans-adjusts the amount of light going into the
objective lens
Microscope- Nosepiece Correct Ans-holds the objective lenses and rotates to change from
one objective to another
Microscope- Coarse Objective Knob Correct Ans-moves the stage larger distances to help get
the object in focus
Microscope- Fine Adjustment Knob Correct Ans-moves the stage smaler increments to help
get the object in better focus
Microscope- Objective Lens Correct Ans-magnifies the object. It is located near the object.
Microscope- Occular Lens Correct Ans-magnifies the image of the object from the objective
lens. It is located near the eye.
Steps in using the microscope Correct Ans-1) scanner power in place
,2) place slide of specimen stage in place with stage clips
3) Using the course adjustment knob, raise the stage all the way up and then down slowly until
you can see image of specimen
4) Readjust with fine adjustment knob
Describe the purpose of the oil immersion lens Correct Ans-Used when oil is added to the
slide. Oil must touch the object and objective lens to that the light does not refract futher
Parfocal Correct Ans-Parfocal microscopes are able to move from one objective to the next
and still be in focus due to the length of the objective lenses
Resolution Correct Ans-The ability to distinguish between two objects that are very close
together.
What is resolving power? Correct Ans-The measurement of resolution
What are two ways to increase resolving power? Correct Ans-1. By decreasing the
wavelength of light (using a blue filter) 2. Increasing the numerical aperature
What units are used to express resolving power? Correct Ans-nm or nanometers
What is better, smaller or larger resolving power? Correct Ans-Smaller is better
Light microscopes have a 200nm resolving power
, Electron microscopes have a .2nm resolving power
What is chromatic aberration? Correct Ans-The effect when many colors are seen toward the
edge of the microscope field of vision (like a prisim)
How are microscopes corrected for chromatic aberration? Correct Ans-With a special
achromatic lens (corrected for red and blue light) or by using a blue filter. The lab has blue filters
in their microscopes which also increase resolution.
Describe the process of making a wet-mount slide Correct Ans-1) Add the specimen to the
slide
2) Touch the edge of the cover slip with one edge of drop of specimen.
3) Let the cover slip drop gradually to the slide, covering the drop of specimen.
Describe the purpose of making a wet-mount slide Correct Ans-To be able to see living
organisms under the microscope in their natural state.
What is the advantage of using a wet-mount slide? Correct Ans-Can see movement and
determine if microbes posses their own method of motility. Can also see the actual shape and
arrangement of microbes.
What is the dis-advantage of using a wet-mount slide? Correct Ans-The movement is very
fast, microbes are transparent. Must use a "dark-field stop".
Answers
Microscope- The Condenser Correct Ans-focuses the light ging into the objective lens
Microscope- The Iris Diaphragm Correct Ans-adjusts the amount of light going into the
objective lens
Microscope- Nosepiece Correct Ans-holds the objective lenses and rotates to change from
one objective to another
Microscope- Coarse Objective Knob Correct Ans-moves the stage larger distances to help get
the object in focus
Microscope- Fine Adjustment Knob Correct Ans-moves the stage smaler increments to help
get the object in better focus
Microscope- Objective Lens Correct Ans-magnifies the object. It is located near the object.
Microscope- Occular Lens Correct Ans-magnifies the image of the object from the objective
lens. It is located near the eye.
Steps in using the microscope Correct Ans-1) scanner power in place
,2) place slide of specimen stage in place with stage clips
3) Using the course adjustment knob, raise the stage all the way up and then down slowly until
you can see image of specimen
4) Readjust with fine adjustment knob
Describe the purpose of the oil immersion lens Correct Ans-Used when oil is added to the
slide. Oil must touch the object and objective lens to that the light does not refract futher
Parfocal Correct Ans-Parfocal microscopes are able to move from one objective to the next
and still be in focus due to the length of the objective lenses
Resolution Correct Ans-The ability to distinguish between two objects that are very close
together.
What is resolving power? Correct Ans-The measurement of resolution
What are two ways to increase resolving power? Correct Ans-1. By decreasing the
wavelength of light (using a blue filter) 2. Increasing the numerical aperature
What units are used to express resolving power? Correct Ans-nm or nanometers
What is better, smaller or larger resolving power? Correct Ans-Smaller is better
Light microscopes have a 200nm resolving power
, Electron microscopes have a .2nm resolving power
What is chromatic aberration? Correct Ans-The effect when many colors are seen toward the
edge of the microscope field of vision (like a prisim)
How are microscopes corrected for chromatic aberration? Correct Ans-With a special
achromatic lens (corrected for red and blue light) or by using a blue filter. The lab has blue filters
in their microscopes which also increase resolution.
Describe the process of making a wet-mount slide Correct Ans-1) Add the specimen to the
slide
2) Touch the edge of the cover slip with one edge of drop of specimen.
3) Let the cover slip drop gradually to the slide, covering the drop of specimen.
Describe the purpose of making a wet-mount slide Correct Ans-To be able to see living
organisms under the microscope in their natural state.
What is the advantage of using a wet-mount slide? Correct Ans-Can see movement and
determine if microbes posses their own method of motility. Can also see the actual shape and
arrangement of microbes.
What is the dis-advantage of using a wet-mount slide? Correct Ans-The movement is very
fast, microbes are transparent. Must use a "dark-field stop".
