Oregon State University MB303
Midterm Exam And 100% Solved
Solutions 2025-2026 Updated.
compound microscope - Answer a compound microscope has two types of lenses: ocular and
objectives.
magnification - Answer enlargement of objects
resolution - Answer the ability to distinguish structures separated by short distances.
parfocal - Answer the ability of a microscope to maintain approximate focus when switching
between lenses.
working distance - Answer the distance between the specimen and objective.
refractive index - Answer the angle at which light refracts through a medium
what is the purpose of immersion oil? - Answer to collect aberrant light rays and allow them to
enter the objective.
compare fixed smear vs wet mount slides - Answer Wet mount slides are worse because they
dry after 30-60 minutes and can only be observed under the 10x 40x objectives.
wet mount slides are better because they allow the observer to observe living organisms and
obtain info about motility and natural pigmentation.
why is the phase contrast microscope better than the bright-field microscope - Answer It is
better because it allows us to view details in unstained living organisms.
it does so by separating light into two phases that cancel each other out to form an image.
, basic/cationic dye - Answer the color of the dye is in the positive ion of the dye. These are
generally used in simple stains
acidic/anionic dye - Answer the color of the dye is in the negative ion of the dye
general morphology of bacteria (3) - Answer -bacilli
-cocci
-spiral
cocci arrangements - Answer -diplococci = two cocci
-streptococci = chains of four or more
-staphylococi = grape clusters
-tetrads = packs of four cocci
groups of spiral bacteria - Answer -spirochetes = extremely thin flexible rods with several
curves
-spirilla = rigid rods with several curves
-vibrios = short curved bacteria.
4 types of media and their advantages/disadvantages? - Answer broth medium
agar slants
agar deeps
agar plates
what is a RODAC plate and what is it used for? - Answer It is a special plate with 1% extra agar
to make it convex. It is used for environmental sampling of bacteria from a flat surface.
what is the swab technique and what is it used for? - Answer It is used for environmental
sampling of irregular surfaces. It involves using a sterile swab to sample the environment.
how are the results of RODAC plates and swab techniques interpreted? - Answer they are
plated on agar (in the case of swab method) and the colonies are counted. They are then
considered to be of acceptable sanitation with <100 colonies, or <10 in the case of the swab
Midterm Exam And 100% Solved
Solutions 2025-2026 Updated.
compound microscope - Answer a compound microscope has two types of lenses: ocular and
objectives.
magnification - Answer enlargement of objects
resolution - Answer the ability to distinguish structures separated by short distances.
parfocal - Answer the ability of a microscope to maintain approximate focus when switching
between lenses.
working distance - Answer the distance between the specimen and objective.
refractive index - Answer the angle at which light refracts through a medium
what is the purpose of immersion oil? - Answer to collect aberrant light rays and allow them to
enter the objective.
compare fixed smear vs wet mount slides - Answer Wet mount slides are worse because they
dry after 30-60 minutes and can only be observed under the 10x 40x objectives.
wet mount slides are better because they allow the observer to observe living organisms and
obtain info about motility and natural pigmentation.
why is the phase contrast microscope better than the bright-field microscope - Answer It is
better because it allows us to view details in unstained living organisms.
it does so by separating light into two phases that cancel each other out to form an image.
, basic/cationic dye - Answer the color of the dye is in the positive ion of the dye. These are
generally used in simple stains
acidic/anionic dye - Answer the color of the dye is in the negative ion of the dye
general morphology of bacteria (3) - Answer -bacilli
-cocci
-spiral
cocci arrangements - Answer -diplococci = two cocci
-streptococci = chains of four or more
-staphylococi = grape clusters
-tetrads = packs of four cocci
groups of spiral bacteria - Answer -spirochetes = extremely thin flexible rods with several
curves
-spirilla = rigid rods with several curves
-vibrios = short curved bacteria.
4 types of media and their advantages/disadvantages? - Answer broth medium
agar slants
agar deeps
agar plates
what is a RODAC plate and what is it used for? - Answer It is a special plate with 1% extra agar
to make it convex. It is used for environmental sampling of bacteria from a flat surface.
what is the swab technique and what is it used for? - Answer It is used for environmental
sampling of irregular surfaces. It involves using a sterile swab to sample the environment.
how are the results of RODAC plates and swab techniques interpreted? - Answer they are
plated on agar (in the case of swab method) and the colonies are counted. They are then
considered to be of acceptable sanitation with <100 colonies, or <10 in the case of the swab
