If a Black Hole Is Truly Black and Has an Escape

question 63

Multiple Choice

If a black hole is truly black and has an escape velocity greater than the speed of light such that no light can escape it,where do the X-rays come from in the black hole candidates so far identified?

• A) From stars behind the black hole,whose light is focused and concentrated by gravitational focusing to the point where it becomes X-ray radiation
• B) The black hole is only black to visible radiation traveling at the speed of light,but because X-rays travel faster than the speed of light,they can escape.
• C) From the normal star accompanying the black hole,its ordinary light being blueshifted into the X-ray spectral region by the intense gravity of the black hole
• D) From the matter surrounding the black hole,which is highly condensed and hence very hot

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Definitions:

Cost Principle

An accounting principle that states assets should be recorded at their cost at the time of purchase, not their current value.