The scattering of light in quartz
When a plane-polarised beam of the intense λ 2537 radiation from a water-cooled, magnet-controlled mercury arc is sent along the optic axis of a perfectly clear and transparent sphere of quartz crystal free from inclusions, the track when photographed from a direction transverse to the beam exhibits striking fluctuations in intensity along its length. The effect, which is reproduced in the paper, is obviously connected with the rotation of the plane of polarisation of the polarised λ 2537 radiation as it traverses the crystal. The distance between one dark band to the next corresponds closely to a rotation of 180° of the plane of polarisation of the λ 2537 radiation. A similar effect was observed and photographed in smoky quartz by the present Lord Rayleigh in 1919 using the Tyndall scattering of visible light by the inclusions in the crystal. In the present case the effect is due to the diffusion of light arising from the atomic vibrations in the crystal lattice, and the clearness of the bands indicates that such scattering is strongly polarised.