The factor most directly responsible for making a black hole invisible is its A) size. B) mass. C) color. D) surface escape velocity. E) none of these

Question

The factor most directly responsible for making a black hole invisible is its

A) size.

B) mass.

C) color.

D) surface escape velocity.

E) none of these

Answer 1

Surface escape velocity is responsible for being invisible.

Escape velocity formula, ve = sqrt(2GM/R)

if ve = c (the velocity of light), then c^2R = 2GM.

that is even light can not escape once it enters the event horizon of the black body.

Mass and size does not matter directly. if we squeeze our earth to about 8 mm in size it becomes black hole.

But naturally when stars of mass more than 5 solar mass goes through a supernova explosion black holes form. If it is about 3 solar mass neutron stars born.

Any way the gravity of the object has to be so high that even light can not escape then we call that object a black hole.