However, it is usually possible for humans to avoid wide-open positions by conservative play, and to angle for strategic positions in which computers fare worse.
Rays that meet the core-cladding boundary at a high angle (measured relative to a line normal to the boundary), greater than the critical angle for this boundary, are completely reflected.
The critical angle (minimum angle for total internal reflection) is determined by the difference in index of refraction between the core and cladding materials.
