My teacher said "Red apple is red because it absorb all light and reflect only red while our eyes can detect all light"

I know that all object/thing made of atoms so different atoms are the source of different color.

My main question is: "How can atoms reflect different colors? Is it because electron excitation and de-excitation?"

  • $\begingroup$ Alright that answers some of my question, so atoms absorb all light then re-emit it ? Does that happen immediately ? Another question if electron was in the outermost level of an atom will it go into higher level or will it be free ? $\endgroup$ – Mahmoud Usama Fawzy Feb 10 '19 at 15:38
  • $\begingroup$ If we are talking about visible light then I doubt the radiation is ionizing. $\endgroup$ – BioPhysicist Feb 10 '19 at 15:45
  • $\begingroup$ So visible light just excite electron to go higher level then electron emit visble light "with certain frequency/color" and get back to its level that how color works ? $\endgroup$ – Mahmoud Usama Fawzy Feb 10 '19 at 15:51
  • $\begingroup$ This question is obviously too broad. Anyways, I can tell you that color does not only depend on the atoms, but also on the molecules and its structure. $\endgroup$ – FGSUZ Feb 10 '19 at 21:09

Light is electromagnetic radiation . Electromagnetic radiation of a single frequency is in a one to one correspondence with the color scheme of the rainbow spectrum for visible frequencies. With a definite frequency of visible light, the color we see is determined by the location of the frequency in the spectrum.


White light is not identified with a single frequency , it is a mixture of many frequencies.Viewing colors is a biological process that depends on how the rods in the retina perceive color, it is called color perception..

The color of the apple does depend on the reflected frequencies when illuminated by white light, but "white light" contains many frequencies and how these are absorbed and reflected by the apple and how the are perceived by the eye is a complex process that includes many frequencies that build up the perception of the colors identified as "red for an apple". Percieved red contains many frequencies as seen below.

color perception

So it is more complicated than absorption and refection by atoms, reflections and absorptions play the primary role but the color perceived depends on biology.

Excitation of the surface atoms and molecules and deexcitations play a smaller role because directionality is lost in reemission after absorption.

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  • $\begingroup$ Does the photon really reflect or atoms absorb it and emits different photon ? $\endgroup$ – Mahmoud Usama Fawzy Feb 10 '19 at 15:57
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    $\begingroup$ Careful with the wording. The relationship between color and frequency is not one-to-one. 1.) most colors cannot be associated with a single frequency. 2.) as your graphic points out, "The combination of light wavelengths to produce a given perceived color is not unique". $\endgroup$ – garyp Feb 10 '19 at 17:01
  • $\begingroup$ @garyp well, I edited. $\endgroup$ – anna v Feb 10 '19 at 17:57
  • $\begingroup$ @MahmoudUsamaFawzy From solid surfaces it is mostly reflection , because absorption and reemission takes place in a spherical distribution and most of the energy will not arrive in the eye. $\endgroup$ – anna v Feb 10 '19 at 18:00
  • $\begingroup$ garyp's comment still not being fully appreciated ... $\endgroup$ – Paul Young Feb 10 '19 at 19:02

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