- Prepared slide with 3 colored, crossed threads
- Place a slide containing 3 colored and crossed threads on the microscope
- Determine the width (diameter) of the threads using the procedures from
- Locate a spot where all 3 threads cross each other at the same point. Use
the fine focus control to focus first on the lowermost thread, then the
middle thread, and finally, the uppermost thread. List the order of the
threads from the top to the bottom, by indicating their color.
- Focus on the top of the uppermost thread. Note the scale markings on the
fine focus knob and record the calibrated reading directly from the fine
focus control. Carefully rotate the fine focus and stop when the microscope
is just focused on the upper edge of the next thread. Record the reading
from the focus control below. The difference between the 2 readings is the
depth (thickness) of the upper thread.