One of the most interesting features of these discoveries is the fact that the wavelength dependence of interstellar polarization from the UV to the IR can be characterized by the single parameter Lambda max . There is a well-known relationship between R v and Lambda max , which means that R v can be found from polarization measurements on the blue side of Lambda max . This may prove to be a powerful technique for determining stellar distances within our galaxy. The uncertainty in extinction corrections can cause the largest error in distance determinations of distant stars. It is necessary to know the appropriate value of R v .
R v is difficult to determine.
It is found by determining a complete reddening curve extending as far into the infrared as possible, or in clusters with variable reddening from the slope of the apparent distance modulus vs. color excess. Neither technique is possible for single distant stars. It seems likely that a polarization index can be developed that will permit extinction corrections to be determined. This has some exciting ramifications for future developments in polarimetry. An interesting result is that if polarization magnitude divided by extinction is plotted vs. wavelength, a linear relation from 1300A to beyond 10000A except for a dip at 2200A is found.