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Reflection on black surfaces

  1. Feb 19, 2004 #1
    black surfaces apparently absorbs all light, thats why it appears black, but does it ever reflect light off its surface?
    what if its a polished black suface..we could actually see our own reflection on these surfaces.. so is there light being reflected at all? is there any difference from the usual reflection???
  2. jcsd
  3. Feb 19, 2004 #2


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    Something perfectly flat black will reflect no light at all and would essentially be invisible. Such a surface is simply unattainable.

    The difference between glossy and flat is that glossy reflects light more or less at the macroscopic angle of incidence. So since no black surface will ever be perfect, they can be polished to reflect like a mirror.
    Last edited: Feb 19, 2004
  4. Feb 21, 2004 #3
    How does a perfectly black surface become 'invisible'. Are you suggesting that it becomes transparent? I thought it would still be black.
  5. Feb 21, 2004 #4


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    I think he means that your eyes will receive no light coming from there, which is true. However, as you say, your brain will clearly distinguish that pattern in your retina and label it as "black", which means that you will "see" it.
  6. Feb 21, 2004 #5
    i believe the closest attained [by a special paint] was something like 97 or 98%...pretty damn close, but not quite there yet
  7. Feb 22, 2004 #6


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    In a broader sense, nothing is 'black', nor can anything be perfectly black (except for black holes). If an object absorbs light, it will get a little hotter, and so it will emit a little more in the infrared (this is a simplification). If our eyes could 'see' IR, we may find that 'black' objects were actually among the brightest objects!
  8. Feb 22, 2004 #7
    If I recall it properly, the reason why you see "Black" is really because your retinas cannot process (see) a certain color (wavelength) of Violet, at the bottom end of the visible light scale...

    Then again, it is a bit like looking up at the night sky (away from cities where you could see those old fashioned things called "Stars") inasmuch as, you think, in your mind, that you see the "inky blackness of outer space", and you have fooled yourself completely! as what you are looking at is chock a block FULL of light, just that, you cannot see light, you only 'see' light when reflecting/interacting off/with a surface....light, when in motion, is completely invisible!

    (If you doubt that, just look at/in the space between the lamp and the table...you do not see the light travelling!)
  9. Feb 23, 2004 #8
    Even black holes have Hawking Radiation, but it's effectively black.

    Things can look perfectly black to the human eye even if they are not truly black because there is a lower limit for photons hitting the retina for it to register.
  10. Feb 23, 2004 #9


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    Welcome to Physics Forums Iron Sun X!

    Did you take the solar eclipse photo in your avatar?
    both an upper and lower frequency limit, and a photons per second limit in either retina (retinal signals are not additive).
    Last edited: Feb 23, 2004
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