Calculation Of The Dispersion - PCE Instruments AR3 Betriebsanleitung

7. Calculation of the Dispersion

The dispersion value can be calculated from the follow-
ing equation:
nF - nC = A + B x a
The values A and B in table 2 are related to refractive
indices. The values in between are to be obtained by
interpolation.
The refractive index of the sample must be measured,
the values appertaining to A and B are to be taken from
table 2.
The value for A is determined as follows:
When measuring the refractive index, the colour on the
dividing line is eliminated by using the compensation
knob. There is a scale ring on the knob which is divided
into 60 – 0 – 60.
There are two positions on the compensation knob
where it is possible to eliminate the colour fringe on the
dividing line.
Adjust to the two positions and read the corresponding
value on the scale ring on the compensation knob.
This process should be repeated several times and the
values noted on a table so that the mean value can be
calculated.
The alpha value can then be determined using the
mean value „Z" according to table 3. The values in
between can be found by interpolation.
The Abbe figure is another important quantity as an
identification of an optical medium. It is calculated as
follows:
V =

7. Calculation of the Dispersion

n
-
D 1
n n
-
F C
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