Plexiglass Spiral With Laser
To demonstrate total internal reflection with laser light.
Plexiglass spiral with laser.
Due to total internal reflection the light from the laser remains mostly confined within the spiral plexiglass rod,and only exits at the end, where the angle between the surface and the incoming light exceeds the critical angle. Actually, some light escapes at scratches along the spiral, as can be seen in the photograph.
Peter J. Cumpson, Light Scattering by Fibers: An Analysis Using the Partial Wave Phase-shift Formalism of Quantum Mechanics,AJP 58, 659-663, (1990).