MICROBIOLOGY LAB EXAM 1
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS ALREADY
PASSED!!!
What is the function of the condenser on a light microscope?
✔✔ Focuses the cone of light passing through the specimen and directly into the
objective lens.
What is the function of the iris diaphragm?
✔✔ Adjusts the amount (intensity and angle) of light passing into the condenser
and objective lens to optimize contrast and resolution.
What is the role of the microscope's nosepiece (revolving nosepiece)?
✔✔ Holds the objective lenses and rotates smoothly to allow the user to switch
between different magnification powers.
What is the function of the coarse adjustment knob?
✔✔ Moves the stage larger vertical distances rapidly to bring the specimen into
rough focus (used primarily with low-power objectives).
What is the function of the fine adjustment knob?
✔✔ Moves the stage in very small, precise increments to achieve sharp, high-
resolution focus (used with high-power and oil-immersion objectives).
Microscope- Objective Lens -ANSWER✔✔magnifies the object. It is located near
the object.
Microscope- Occular Lens -ANSWER✔✔magnifies the image of the object from
the objective lens. It is located near the eye.
Steps in using the microscope -ANSWER✔✔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 -ANSWER✔✔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 -ANSWER✔✔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 -ANSWER✔✔The ability to distinguish between two objects that are
very close together.
What is resolving power? -ANSWER✔✔The measurement of resolution
What are two ways to increase resolving power? -ANSWER✔✔1. By decreasing
the wavelength of light (using a blue filter) 2. Increasing the numerical aperature
What units are used to express resolving power? -ANSWER✔✔nm or nanometers
What is better, smaller or larger resolving power? -ANSWER✔✔Smaller is better
Light microscopes have a 200nm resolving power
Electron microscopes have a .2nm resolving power
, What is chromatic aberration? -ANSWER✔✔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? -ANSWER✔✔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 -ANSWER✔✔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 -ANSWER✔✔To be able to see
living organisms under the microscope in their natural state.
What is the advantage of using a wet-mount slide? -ANSWER✔✔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? -ANSWER✔✔The
movement is very fast, microbes are transparent. Must use a "dark-field stop".
What is a producer? -ANSWER✔✔Are autotroph organisms that make their own
food (through photosynthesis).
What structure is an indicator of a producer? -ANSWER✔✔Chloroplasts is an
indicator that an organism is a producer.
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS ALREADY
PASSED!!!
What is the function of the condenser on a light microscope?
✔✔ Focuses the cone of light passing through the specimen and directly into the
objective lens.
What is the function of the iris diaphragm?
✔✔ Adjusts the amount (intensity and angle) of light passing into the condenser
and objective lens to optimize contrast and resolution.
What is the role of the microscope's nosepiece (revolving nosepiece)?
✔✔ Holds the objective lenses and rotates smoothly to allow the user to switch
between different magnification powers.
What is the function of the coarse adjustment knob?
✔✔ Moves the stage larger vertical distances rapidly to bring the specimen into
rough focus (used primarily with low-power objectives).
What is the function of the fine adjustment knob?
✔✔ Moves the stage in very small, precise increments to achieve sharp, high-
resolution focus (used with high-power and oil-immersion objectives).
Microscope- Objective Lens -ANSWER✔✔magnifies the object. It is located near
the object.
Microscope- Occular Lens -ANSWER✔✔magnifies the image of the object from
the objective lens. It is located near the eye.
Steps in using the microscope -ANSWER✔✔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 -ANSWER✔✔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 -ANSWER✔✔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 -ANSWER✔✔The ability to distinguish between two objects that are
very close together.
What is resolving power? -ANSWER✔✔The measurement of resolution
What are two ways to increase resolving power? -ANSWER✔✔1. By decreasing
the wavelength of light (using a blue filter) 2. Increasing the numerical aperature
What units are used to express resolving power? -ANSWER✔✔nm or nanometers
What is better, smaller or larger resolving power? -ANSWER✔✔Smaller is better
Light microscopes have a 200nm resolving power
Electron microscopes have a .2nm resolving power
, What is chromatic aberration? -ANSWER✔✔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? -ANSWER✔✔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 -ANSWER✔✔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 -ANSWER✔✔To be able to see
living organisms under the microscope in their natural state.
What is the advantage of using a wet-mount slide? -ANSWER✔✔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? -ANSWER✔✔The
movement is very fast, microbes are transparent. Must use a "dark-field stop".
What is a producer? -ANSWER✔✔Are autotroph organisms that make their own
food (through photosynthesis).
What structure is an indicator of a producer? -ANSWER✔✔Chloroplasts is an
indicator that an organism is a producer.
