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Problem about black body

  1. Jun 30, 2009 #1
    if something is black in color, that means it doesn't reflect light(photon)?
    where do this light got?

    also for black hole
    why people say that the gravity of black hole is so strong the light cannot escape?
    Is it means that gravity can affect em wave?Thank you~

    Of topic problem...
    (crazy idea)
    is there any process that mass converse to charge or the reverse case?
  2. jcsd
  3. Jun 30, 2009 #2
    mass converting to charge doesn't really make a whole lot of sense. An electron, for example has both mass and charge. You can't have charge without mass. However, mass can be converted to energy and energy can then convert to particle pairs (like a positron and an electron). However, energy AND charge must always be conserved so you can never create an imbalance of charge.

    As for black holes, yes gravity effects light. That is what general relativity is all about (space-time distortion and such). You may be confused because you may have learned newton's law of gravitation which is only dependent on mass (and light has no mass). However, despite being an excellent approximation newton's view of gravity is wrong and was replaced by einstein's theory of general relativity.
  4. Jun 30, 2009 #3
    As for the color black... Yes, TRULY black things absorb all light (this light energy usually goes into heating the object up which is why when you were a black t-shirt out in the hot sun you get hotter than a white t-shirt). However, most things that we call 'black' are only partial absorbers, they reflect some back (which is why most things that are 'black' don't, truly, look like darkness). However, since they play no favorite with which light they reflect (which is how other things acquire color) and because they absorb a chunk of reflecting light, they look black.
  5. Jun 30, 2009 #4


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    Black is the absence of light, so you are correct. Intruding photons are either absorbed or pass right through. Black holes do forbid photons from escaping from inside their event horizons. Photons are, however, freely emitted from matter approaching the event horizon of a black hole. White holes? Highly unlikely based on observational evidence.
  6. Jun 30, 2009 #5
    Welcome to PF, anson !!

    Enjoy your ride. You will find many things here.
  7. Jun 30, 2009 #6
    thz everyone
    actually, l am thinking of something crazy.
    To unify gravition and em , we need some phenomenons of the interaction of gravition between em. Black hole affect light. Can this be the right phenomenon for the interaction of gravition between em? Actually, is there any more phenomenon?

    Another problem about light is that will light die out if light don't experience any reflection?
  8. Jun 30, 2009 #7
    I don't know what you mean by unifying gravity and em. And no, light does not diminish unless it comes in contact with something.
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