a. Performance Check
(1) Place one TI on another and place on base of monochromatic light (fig. 1).
Figure 1. Monochromatic light - equipment setup.
A black cloth or paper placed under bottom TI will make the
band more distinctly readable.
(2) Locate thread as shown in figure 2 and pull taut. Read and record deviation
from straight line of fringes under monochromatic light.
Bands should be viewed as near a vertical position as possible.
Use monochromatic light only when required.
(3) Rotate the TI (both flats) approximately 90 degrees and repeat (2) above.