Escape Velocity & Black hole
The topic BLACK HOLE, itself grabs the curiosity of the people. 
It is the most strange phenomena that has been existing all over the universe.
In simple language, black hole is the “death star” . In addition, when any objects (even light) passes through the gravitational field of black hole, it absorbs those objects . And by object, it could be anything. Even light cannot escape its gravity.
As everybody knows about the “EVENT HORIZON” which is the boundry of blackhole’s gravitational field. Once the object reaches to the event horizon of the blackhole, than it just absorbs and makes the object invisible. Even it absorbs light and makes it invisible. Why does it happen? Here starts the explanation interms of ESCAPE VELOCITY.
(By invisible, it means that in order to see any object, the light must strike through our eyes retina so that the brain receptors makes an image we see, since the light doesn’t return back from event horizon, it makes the object invisible)
In physics, escape velocity is the minimum speed required for an object to escape from the gravitational influence of a massive body, that is, to achieve an infinite distance from it. Escape velocity is a function of the mass of the body and distance to the center of mass of the body. The earth’s escape velocity is 11.19km/s. Which means, any object has to travel at the speed of 11.19k/S in order to escape the gravitational boundry of the earth. Once the object reached the escape velocity of earth, it reaches out of the earth’s gravitatonal field which means, the earth’s gravity doesn’t affect the object once it escapes to the space acquiring its escape velocity.
In the same way, the event horizon which is also called as “point of no return” , surrounds the blackhole and has the escape velocity equal to the speed of light, which is 3×10^8m/s. That means, any object in the event horizon, has to exert the velocity more than the speed of light inorder to escape its gravitational field. But unfortunalety, nothing can travel faster than the speed of light. Thus, even light cannot escape from the event horizon of blackhole
