Graticule Flashcards
What is an eyepiece objective lense
Special eyepiece lens that contains a scale
Before measurements are made what must be done
Eyepiece graticule needs to be calibrated before measurements and made
Why does it need to be calibrated
The eyepiece scale will represent different lengths depending on the magnification use
Whitt what is it calibrated
A stage micrometre which is a special slide that has a calibrated scale of no length on its upper surface
1mm
10 micrometers
1cm
100 micrometers
Procedure
I
Calibrating at high power
The appearance of the eyepiece graticule not change the stage micrometre will become magnified much more than the full length of the scale will no longer visible within the field view
What to do once the calibration is complete
Remove the stage micrometre and replace it with the specimen slide containing the cells to be measured
How to tell between the two scales at low power
If you are just the focusing of the stage micrometre will come in and out of focus of the eyepiece graticule is unaffected
If you rotate the eyepiece lens the eyepiece graticule will also rotate the stage micrometre is unaffected
Why choose high power power
This increases the precision and therefore the accuracy of the measurement. Reliability can be increased by taking several measurements
How to improve accuracy and reliability when doing cell length measurements
Consistent in deciding what the link is e.g. for this extent of the sale and as far as the middle lamella between adjacent cells. Reliability by measuring a number of cells
How to estimate cell length quickly
Low powers it is possible to estimate the width of the field of view when looking into a microscope by focusing on a transparent ruler. You can then estimate cell length by estimating the proportion of the diameter of the view that the cell covers
