Total reflection phenomenon

Contrary to the behavior of the visible light photons, for X-rays any medium is less dense than vacuum and any solid is optically less dense than air. This results in a refracted beam deflected toward the interface. Following this logic, one can see that there is a minimum critical angle α₁ = α_crit for which refraction is just possible. For angles α₁ smaller than α_crit no beam enters the medium 2. The interface behaves like an ideal mirror and completely reflects the incident beam back into the medium 1. This phenomenon is called Total Reflection.