EXERCISE 2: OCULAR MICROMETER Flashcards
TRUE OR FALSE
Any laboratory doing diagnostic work
in parasitology should have a
calibrated microscope available for
precise measurements.
TRUE
This is also known as the reticule, Measurements of objects microscopically are made with an ____, a disc made of glass that is inserted into the eyepiece of the microscope.
ocular micrometer
TRUE OR FALSE
The micrometer disc is etched with a
measuring scale which is evenly divided
into 50 or 1000 units
FALSE
“100 UNITS”
A- FIRST TRUE
B-SECOND TRUE
C-BOTH TRUE
D-BOTH FALSE
The scale on the ocular
micrometer represents different
measurements as it changes with total
magnification, and thus has no absolute
value.
Therefore, the ocular micrometer
does not have units
C
looks like a glass slide but has a scale of known true length etched on the surface
stage micrometer
typical stage micrometer scale is
1.0 mm long (etched with divisions of 0.01
mm)
A- FIRST TRUE
B-SECOND TRUE
C-BOTH TRUE
D-BOTH FALSE
the stage micrometer is focused with an objective (usually starting with the lowest power) of the microscope
The eyepiece can be rotated and
the stage micrometer is moved on the microscope stage so that the two scales are
parallel to each other.
C
[SEQUENCING]
Remove the eyepiece from the microscope and unscrew the top or bottom lens, depending on its construction. Place the ocular scale on the diaphgram within the eyepiece with the etched surface on the undersurface of the reticule. Screw back the lens and re-insert the eyepiece into the microscope.
Place the stage micrometer on the microscope stage and focus the low-power objective on some portion of the scale with the 10x eyepiece.
Adjust the micrometer by moving by moving the stage so that the 0 line of the ocular micrometer is exactly superimposed on the 0 line of the stage micrometer.
Without moving the stage micrometer, find another point at the extreme right where two other lines are exactly superimposed. This second set of superimposed lines should as far to the right as possible from the 0 lines. This distance will vary with the objective used. At higher magnifications, the thickness of the etched lines may be great that you need to look for superimposition of either left or right edge of the individual lines.
Count the number of division lines on the ocular micrometer between the 0 line and the point where the second set of lines is superimposed.
Then count the number of 0.1 mm division lines between the 0 line and the second superimposed line the stage micrometer
Calculate the length represented by the ocular unit
Prepare a simple chart
1,2,3,4,5,6,7,8
A- FIRST TRUE
B-SECOND TRUE
C-BOTH TRUE
D-BOTH FALSE
Each objective of the microscope must be calibrated separately.
Therefore, the
calibration factor is different at each magnification.
C
TRUE OR FALSE
After each objective has been calibrated, the oculars containing the disc and/or
these objectives can be interchanged with corresponding objectives or oculars
on another microscope.
FALSE
“CANNOT BE INTERCHANGED”
A- FIRST TRUE
B-SECOND TRUE
C-BOTH TRUE
D-BOTH FALSE
The eyepiece containing the ocular micrometer can be stored until needed.
Post the calibration factor for each objective either on the base of the microscope
or on a nearby wall or bulletin board for easy reference.
C
TRUE OR FALSE
Calibration is usually repeated weekly.
FALSE
“repeated annually”
TRUE OR FALSE
When the high dry and oil immersion objectives are used, the 0 line of the stage
micrometer will increase in size, whereas the ocular 0 line will remain the same size.
TRUE
