What is Colour?

  1. Hi,

    I'm confused about what should really be a simple explanation. What is colour? I've been told that it is because different materials absorb and reflect different colours of light (i.e. different wavelengths between 380 and 740 nm, the spectrum of visible light), but what gives a material this property to absorb and reflect light? In terms of the particles, why is this the case?

  2. jcsd
  3. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

    Orbiting the atoms are electrons, if you put in a photon (of light) you give energy to an electron and it moves up to a higher level, absorbing (destroying the photon). Similarly an electron can give off a photon by dropping to a lower level.

    The trick is that only certain levels are allowed, and so only fixed differences in energy, and so fixed energies (=wavelength) of photons.
    Each type of atom, and molecule has different energies and so absorbs and emits different colours.

    Then your brain has a lot to do with what colour you see when you eye detects certain wavelengths.
  4. This answers the inquiry pretty well, but I'd also like to add that radiators of light possess what's called a 'fine structure', which is the very narrow band of energy levels the electron drops back down to. The fact that electromatic radiators do so discreetly (why else would there be a fine structure? In other words, why else would an E/M radiator radiate such a narrow band of freequencies?) all but proves that there is electron activity in the atom whereby the electron of the atom is jumping up and back down defined and discreet energy levels.
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