Final answer:
The ISCO for light coincides with the ISCO for matter around a non-rotating black hole, which is at a distance of 3 times the Schwarzschild radius. For rotating black holes, the ISCO can vary depending on the black hole's rotation and angular momentum.
Step-by-step explanation:
The Innermost Stable Circular Orbit (ISCO) for light is located at the same radius as the ISCO for matter. In the context of black holes, both light and matter are influenced by the same gravitational forces determined by the black hole's mass and rotation. Therefore, at the ISCO, which is fundamentally determined by these forces, the paths of both light and matter cannot maintain a stable orbit and will spiral inwards towards the black hole. It is worth noting that for non-rotating (Schwarzschild) black holes, the ISCO for matter and light coincides, which is a distance of 3 times the Schwarzschild radius from the center of the black hole. However, for rotating (Kerr) black holes, the ISCO can vary depending on the direction of the rotation and the angular momentum of the black hole.