How Does a Mirror Work and Why Doesn't It Look Blue?

[ashishsinghal]

I have learned that when light falls on an object, the electrons get excited and emit light in return. this gives every object its colour. Is this correct?

So how does a mirror work.

 

[JaredJames]

http://en.wikipedia.org/wiki/Reflection_(physics)

See the section on "Mechanisms of Reflection" onwards.

 

[sophiecentaur]

That Wikkers article could cause confusion if you just consider individual electrons being "excited" by individual photons. If it happened this way then a specular reflection would not occur - this is because the time between excitation and re-emission (as in isolated atoms/molecules) is variable and the re-emitted photons would not be cophased any more. The interaction with the surface has to be viewed more as a bulk interaction - and hence it is more fruitful to talk in terms of waves and induced currents. Now, this is easy to do when talking about radio waves being reflected by a metal screen because we tend to be more familiar with electric currents being associated with radio waves. But we can do the same with light waves as well.
The big difference between what happens with an isolated atom and a solid surface is that the single electron in an atom of Hydrogen gas has widely spaced energy states and interacts one-to-one with a photon whereas the electrons on the surface of a metal have very closely spaced energy states and a single photon of incident energy can be though of as exciting many many electrons at a time. (If you insist on talking photons in this case).

 

[LostConjugate]

A mirror reflects all the colors because it resonates at all frequencies. A colored reflection is a configuration much like your FM radio, where its amplitude is much higher at a specific frequency, where it resonates.

 

[sophiecentaur]

It isn't a "resonance" because. by definition, a resonance is a narrow band thing. It's just a consequence of the fields due to induced currents. The direction of the reflected wave is best predicted by looking at the diffraction at the surface. (Huygens' principle, if you like)

 

[LostConjugate]

When you see an object return only the blue frequency range when you shine all colors on it, that is not a narrow band in the blue frequency?

 

[sophiecentaur]

Does a shiny metal mirror look blue?
In any case, a coloured surface usually looks coloured because of broadband resonant absorption - not resonance and re-radiation of a single spectral frequency.