Eisco-Acrylic-Light-Wave-Guide-Demonstrator-Eisco-PH0587-p-An-S-shaped-220-x-20-x-20mm-acrylic-bar-which-can-be-used-in-conjunction-with-a-ray-box-to-demonstrate-total-internal-reflection-p-Eisco-Acrylic-Light-Guide-Demonstrator-S-Shape-Block-220-x-20-x-20mm