Optical photons transmit with TRANSMISSION = 0 and REFLECTIVITY = 1?

Physics Processes, Models and Cross Sections
2

The issue is the confusing terminology. Neither TRANSMISSION nor REFLECTIVITY mean what one might think they do.

One of 3 things might happen to the photon at the boundary.

  1. It is absorbed.
  2. It passes through the boundary unchanged (same direction, energy)
  3. It interacts according to Snell’s law.

The probability of the photon being absorbed is 1-REFLECTIVITY. The probability of passing through the boundary unchanged is TRANSMISSION.

In your case, with TRANSMISSION=0 and REFLECTIVITY=1, all the photons interact according to Snell’s law. Some undergo total internal reflection and some undergo Fresnel refraction.

I think, if you want a perfectly diffuse and opaque reflector, you want a dielectric_metal surface (maybe this relates to your other question).