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Colors and Reflected Light

  1. Jan 2, 2005 #1
    Forgive me if this is a dumb question but,

    I know that when I see an object's "color" I'm really just seeing the wavelengths of light that weren't absorbed by that object's surface (right?).

    Why then do some colored objects (matte objects, not glossy objects) take on the different color tones of other nearby objects?
    For example, if I put a vibrant red object next to a vibrant blue object, both in a strong diffused light source, why am I able to see red/purple tones in the blue object where it faces the red object (and vice versa)?

    As I understand it, white light strikes the red object and then red light is reflected off of the object while the rest of the light's colors are absorbed. This red reflected light then strikes a blue object nearby which takes on a red/purple tone.
    Why doesn't the blue object absorb this red light like it absorbed the red light from the white light source?

    Thank you in advance for any help you can offer.
  2. jcsd
  3. Jan 2, 2005 #2


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    Because nothing reflects only a single wavelength. The red object reflects mainly red but, to a lesser extent, other wavelengths also, including blue. The blue object reflects mainly blue but other wavelengths also, including red. With such red and blue objects together in a white light, the red object will reflect light from the white light but also light that has already reflected from the blue object- in other words, there is more blue "in the light" before it reflects off the red object.
  4. Jan 2, 2005 #3
    Nice question ,Eprph , but are you SURE that what you say is correct , most surfaces are not perfect in reflecting or absorbing light. Just because something looks blue ( to be precisely defind) does not imply that it reflects nothing than blue ( to be defined )

    most surfaces are described as being 'strongly ' absorbent or reflective of a limited range of 'colors' i.e. wavelengths , the surfaces considered are not usually ultra simple atomic absorbers such as gasses where individual atoms maybe at work . Most of the time we are talking of atoms, molecules , in a matrix with far more complex 'states' which is why we feel radiative heat as an example .
    All the rules apply -- just the situations are not simple
  5. Jan 2, 2005 #4
    I never thought of it that way. Makes perfect sense though.
    I guess I had just assumed (incorrectly) that all of a particular color was being absorbed.

    Thanks! :smile:
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