The distance of the event horizon from a black hole, known as the Schwarzschild radius, is determined by the mass of the black hole. The Schwarzschild radius represents the point of no return, beyond which nothing, including light, can escape the gravitational pull of the black hole. It is calculated using the following formula:
R = 2GM/c^2
Where: R is the Schwarzschild radius, G is the gravitational constant, M is the mass of the black hole, c is the speed of light.
The event horizon is located at this radius, marking the boundary beyond which objects cannot escape the black hole's gravitational influence. Any matter or radiation that crosses the event horizon is effectively trapped within the black hole.
It's important to note that the Schwarzschild radius is a theoretical calculation based on the assumption that the black hole is non-rotating and uncharged, which is an idealized model known as a Schwarzschild black hole. In reality, black holes can have angular momentum (spin) and electric charge, which affects their properties and modifies the event horizon. However, for non-rotating and uncharged black holes, the Schwarzschild radius accurately represents the distance of the event horizon.