Interactive Java Tutorials Refractive Index Determination
Oblique illumination is sometimes utilized as an alternative to
the Becke line test to determine whether the refractive index of
a specimen is higher or lower than that of the surrounding
medium. This interactive tutorial explores how variations in the
refractive index of a specimen and its surrounding medium alter
visibility in the microscope when utilizing oblique illumination
techniques. The tutorial initializes with a specimen having a
refractive index of 1.15 positioned in a surrounding medium of
refractive index 1.33 (representing water or lightly buffered
aqueous saline solution), and being illuminated with off-axis
light rays originating from the lower left-hand side of the
tutorial window. In order to operate the tutorial, translate the
Specimen (refractive index value) slider between values of 1.0
and 1.5. As the slider is moved from right to left, the specimen
appearance is altered in the Eyepiece View window. To change the
refractive index