| n = | √ | N² - sin²i. |
For convenience the values of n for all usual values of i are computed once for all and arranged for use in tabular form. The latest model of Pulfrich’s apparatus, arranged both for liquid and solid bodies, and also for spectrometric observation is shown in [Fig. 89].
When the sodium light is used it is placed behind the apparatus and the light is collected and reflected on the refractive prism by the lens N. Through H and G is secured the micrometric reading of the angle on the scale D by means of the telescopic arrangement F E. For regulating the temperature of the oil and adjacent parts, a stream of water at any desired temperature is made to circulate through L and S in the direction indicated by the arrows. The manner in which this is accomplished is shown in the cross section of that part of the apparatus as indicated in [Fig. 90].
Fig. 89.—Pulfrich’s New Refractometer.
Fig. 90.—
Heating Apparatus
for Pulfrich’s
Refractometer.
Fig. 91.—Spectrometer Attachment.