New Supersonic Phenomena

Abstract

POLARIZED light has been used for determining the propagation of stress waves in solids for some time. We have employed it to study the propagation of stress waves in glass and plastics and have found what we believe to be evidence of new supersonic phenomena. The experimental arrangement follows classical lines, using ‘Polaroids’ and quarter-wave plates that give circularly polarized light through the transparent sample. For illumination, we used a 1530 PI discharge tube (General Radio) with an effective flash duration of 2 µsec. The transparent sample was loaded by exploding small amounts of lead azide with an electric ‘bridge’. The timing between the flash and the explosion was achieved by a suitable electric timer which allowed a variation of the delay from zero to 30 µsec. It is well known that shock loading causes a compressional and a shear wave to be propagated in the material, both of which essentially follow the so-called Huygens construction.