116
Light Waves and Theib Uses
examining separately the vertical vibrations alone and the horizontal vibrations alone is represented at N, and consists merely of a Nicol prism which can be rotated about a horizontal axis.
With this arrangement a different set of visibility curves
was obtained. These are shown in Figs. 83, 84, 85.
The upper curve of Fig. 83 represents the visibility curve produced by the horizontal vibrations of the red cadmium light in a strong magnetic field. For the vertical vibrations the visibility curve is something totally different, and is shown in the lower half of the figure. The effect of the field is readily appreciated by comparing this figure with Fig. 66, which corresponds to the red cadmium line without any magnetic field.
The upper curve of Fig. 84 represents the visibility curve of the blue cadmium vapor when the horizontal vibrations only are allowed to pass through. When vertical vibrations only are allowed to pass through, the curve has the form shown in the lower half of the figure.
The case of the green radiation, when there is no field, is shown in Fig. 67 above. When the magnetic field is on, and when the horizontal vibrations only are allowed to pass through, the visibility curve has the form of the upper curve in Fig. 85. When vertical vibrations are allowed to pass through, it has the form of the lower curve.
The intensity curves corresponding to Figs. 83, 84, and 85 are shown in Fig. 86. The upper three correspond to
Action of Magnetism on Light Waves 117
the horizontal vibrations, while the lower three correspond to the vertical vibrations. In the case of the red radiations it will be noted that, whether there is a magnetic field or not, there is no particular change for red cadmium light when the horizontal vibrations alone are considered. When the field is on, the vertical vibrations give a double line, or possibly one of more complex form.
In the case of the blue radiations, however, when there is a magnetic field and only horizontal vibrations are allowed to pass through, the line is double. The doubling is very distinct, and the separation is so wide that it should be easily seen by means of the spectroscope. When the vertical vibrations alone are allowed to pass through, there is a very much more complicated effect. In all cases we can see that the line is double, as in the case of red cadmium light, but in this case each component of the double lines is at least quadruple, or even more complex.
In the case of the green radiation, when horizontal vibrations only are considered, we have a triple line for the central line of the Zeeman triplet. When horizontal vibrations alone are allowed to pass through without a magnetic field, it resembles in general character the red line (r/. Fig. 07). When vertical vibrations are examined in the magnetic field, the line is highly complex; and in this case it is absolutely certain that each of the components of the double consists of at least three separate lines. The phenomenon is perfectly symmetrical about the central line.
FIG. 81