The condition for a uniform spherical mass `m` of a radius `r` to be a black hole is [`G` =gravitational constant and `g`=acceleration due to gravity]

Options

A. `((2Gm)/r)^(1//2) lec`
B. `((2Gm)/r)^(1//2)gec`
C. `((2gm)/r)^(1//2)=c`
D. `((gm)/r)^(1//2)gec`

Answer

B

Explanation

A black hole is an object so massive that even light cannot escape from it. This requires the idea of a gravitational mass for a photon, which then allows the calculation of an escape energy for an object of that mass. Escape velocity for that body `v_(e)=sqrt((2Gm)/r)`
`v_(e)` should be more than or equal to speed of light
i.e., `sqrt((2Gm)/r)gec`