A DEVICE TO MEASURE THE AMOUNT OF PLANE POLARIZED LIGHT IN LOW INTENSITY RADIATIONS AND TO MEASURE SMALL ROTATIONS OF THE PLANE OF POLARIZATION

摘要

To investigate polarization properties of radiations too weak to be handled with the common visual devices for the purpose, a photoelectric device is used. A nicol of good quality, with end faces perpendicular to the length is mounted on a caesium vacuum cell, and this, together with the working tube of a two tube bridge amplifier, placed in a brass container free to rotate about an axis passing through the center of the nicol. Control apparatus and the dummy tube and batteries are located in a stationary container, connections being made through a flexible shielded cable. The galvanometer deflection obtained is proportional to the intensity of the component of the radiation able to pass through the nicol. The percent of polarization has been measured with illuminations down to 10-5 foot‐candles. When applied to rotation measurements, a rotation of the plane of polarization of one second of arc can be detected.