Fundamentals of Microbiology (2+2)

Procedure

Mount the ocular micrometer in the eyepiece in position over the bracket in between field lens and eye lens.

Focus the stage micrometer using low power objective and position the ocular micrometer in such a way that the zero line of both ocular and stage micrometer coincides

Calibrate the ocular micrometer against stage micrometer as described before

Repeat the calibration for high power (45 X) objective and for oil immersion (100 X) objective

Record the scale of ocular divisions in micrometer (m) corresponding to different objectives.

Remove the stage micrometer and place the object to be measured. Set the appropriate objective lens and focus.

Measure the no. of ocular divisions that correspond to the length and breadth or diameter of the objects. Express the dimensions in micrometer.

                                                   Known distance between two lines                  

                                                             on  stage micrometer

One division on ocular micrometer in mm =    -----------------------------------------------

                                                                  Number of divisions on ocular micrometer

            Example: if 13 ocular divisions coincide with two stage divisions (2 x 0.01=known distance of 0.02), then

                                                 0.02

One ocular division             = ------------------

                                                  13

                                    = 0.00154mm or 1.54µm.

Observation and Inference: