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Author Topic: black holes and white card.  (Read 1831 times)

paul.fr

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black holes and white card.
« on: 18/02/2008 16:36:19 »
If i had a giant piece of white card, and placed it at the back of a black hole, then shone my torch at the black hole. What would i see?


 

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black holes and white card.
« Reply #1 on: 18/02/2008 18:40:12 »
Assuming that the torch was essentially a point source of illumination  the light from the torch passing a long way away from the hole would provide an even and fading light as the angle to the card got steeper the effect of the hole is to bend the light towards the axis as the gravitational field gets stronger so the light would brighten to a point where it was "focused" on the screen  there would then be some light that was beyond focus and this would add to the fading point of light.  Looking from the card towards the black hole with the torch hidden behind it you would see a bright ring of light somewhat beyond the event horizon.  As you moved away from the axis the light would become uneven and brighter in the direction of the torch and away from it and at some point you would be able to see the torch and an "image" of it on the other side of the hole.
 

paul.fr

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black holes and white card.
« Reply #2 on: 19/02/2008 10:36:31 »
Thanks, Ian. Even I understand that!
 

The Naked Scientists Forum

black holes and white card.
« Reply #2 on: 19/02/2008 10:36:31 »

 

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