# B Black Hole as a Gravitional Lens

1. Jun 10, 2017

### Ashraf Siddiqui

https://en.wikipedia.org/wiki/Gravitational_lens

I want to know about bending light property of a black hole. The bending angle formula
does not tell that r is perpendicular distance to light. Does a black hole
having mass M has different bending power than the body having the same mass M?
What about region around a black hole to bend a light ray? Can we use the above formula in this region?

2. Jun 10, 2017

### Staff: Mentor

The physics in the vacuum outside an ordinary spherically symmetric object of a given mass is the same as the physics in the vacuum outside of a black hole of the same mass. For example, the earth's orbit would be unchanged if we replaced the sun with a one-solar-mass black hole, and the same is true of light deflection by the sun.

3. Jun 19, 2017

### Ashraf Siddiqui

Thanks for your information. I am interested in deflection pattern of light by black hole. Is there any difference in the deflection angle
of light by black hole if :
r is the perpendicular distance from the black hole
& r is the angular distance from the black hole