The test consists of locating the gaps in a graduated series of sizes of incomplete rings whose radial thickness and gap are equal to one-fifth the diameter of the ring.

I had little work experience and few marketable skills when I graduated, and I knew I would have to take a series of unpaid internships before I could find the publishing job I've always wanted.

Measuring birefringence can be accomplished using a "compensator," a calibrated, graduated wedge that is placed in series with the measured item.