Zero pathlength difference

U(l) electromagnetism ( V B 0) predicts that the magnetic field outside the solenoid is zero. Before the current is turned on in the solenoid, there should be the usual interference patterns observed at HI, of course, due to the differences in the two pathlengths. 

The left-hand spectrum in Figure 3.2 shows two peaks that are excellent overlays. Since almost all the absorbances in these two peaks are the same, when they are subtracted they will give a flat line at zero absorbance. In the right-hand spectrum in Figure 3.2, the two peaks to be subtracted are of different sizes. This could be due to differences in pathlength or concentration between the sample and reference. When these two peaks are subtracted the result will have a feature in this region... 

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