Publisher's Synopsis
Excerpt from Infra-Red Transmission and Refraction Data on Standard Lens and Prism Material
The next best prism material is quartz, which is the most use ful in the region of the spectrum extending from the visible to a in the infra-red. Beyond this point a quartz prism is too opaque for practical work.
From the standpoint of dispersion and transparency, a ?uorite prism is the most useful in the region of 2 to 9 it. However, the material is difficult to obtain, and the next best substance is rock salt, which permits measurements to 14 a when using a 60� prism, and to 16 a when using a 30� prism. By inclosing the spectro meter '4 and by keeping the prism covered when not in use, the faces of a rock-salt prism are easily protected from moisture.
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