Several elements might contribute to this unexpected increase in path length. Firstly, the LED strip's inherent non-collimated nature -given its beam angle of around 60° -allows light to enter at varied angles, thereby extending the path length within the medium. Additionally, the tube's curvature and coiling alter the angle at which light hits the air-tube interface, impacting both reflection and, more crucially, refraction. Furthermore, the transparent polymer material of the tube, possessing a refractive index higher than the surrounding air, causes light to refract inward, towards the reaction mixture, effectively lengthening the path.