Question

I would like to know the concept of the reaction of a particle and Anti-particle. How it can occur when approaching blackhole and emit x-rays from it.

Answer 1

I've heard it described (I believe by Lewin) as analogous to destructive interference. If a particle and an anti-particle interfere, their mass is converted to energy (according to e=mc^2) in the form of electromagnetic radiation (light photons).