quarter-undulation

Updated: May 8, 2025

But there is an instrument of very simple construction, called a "quarter-undulation plate," a plate usually of mica, whose thickness is an odd multiple of a quarter of a wave-length, which enables us to discriminate between light unpolarized and circularly polarized.

John Tyndall - Six Lectures on Light: Delivered In The United States In 1872-1873