This question already has an answer here:
We know black holes emit streams of radiation ,also recently discovered that they emit visible light when they eat any nearby matter . "We find that activity in the vicinity of a black hole can be observed in optical light at low luminosity for the first time," astronomer and lead researcher, Mariko Kimura from Kyoto University in Japan, told Charles Q. Choi at Space.com. But it is different from what we normally hear that neither matter nor radiation can escape from black holes. So what's the reason for this.??