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Here's my question: if atoms have well defined energy levels and those differences correspond to the frequencies of light that can be absorbed, how is it that opaque objects absorb all or most visible light frequencies?, frequencies get absorbed and you basically don't have any visible light coming out on the other end.

Shouldn't only those frequencies that have to do with its energy levels get absorbed? Yes, I realize ordinary materials have many different compounds, but surely they don't add up to an infinite number of energy levels? Thanks.

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marked as duplicate by John Rennie, Danu, Kyle Kanos, Brandon Enright, ACuriousMind Aug 25 at 15:50

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If atoms have well define energy levels and the differences correspond to the frequencies of light that can be absorbed,

This is correct

how is it that opaque objects absorb all or most visible light frequencies get absorbed and you basically don't have any visible light coming out on the other end?

The crux of the matter is the word "objects". This means the solid state. You must have noticed that gases are not opaque and liquids also pass a lot of the impinging frequencies. Liquids are in between solids and gases.

Shouldn't only those frequencies that have to do with its energy levels get absorbed?

This is true when atoms are free, once they are joined in molecules many more energy levels appear and some of them going to an infinite continuum even for as simple an atom as the hydrogen atom.as the quantum number n goes to infinity.

Yes I realize ordinary materials have many different compounds, but surely they don't add up to an infinite number of energy levels?

There are an infinite number of possible energy levels. What makes the difference between gases and solids is the possibilities of transition that combinatorially are enhanced and in addition that the impinging radiation can scatter and rescatter inelastically with the combined electric and magnetic fields of the solids until their energy is degraded enough to be absorbed by the soft vibrational and rotational energy levels of the compound.

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If atoms have well defined energy levels and those differences correspond to the frequencies of light that can be absorbed, how is it that opaque objects absorb all or most visible light frequencies get absorbed

Photons in almost all frequencies hitting an object are absorbed in different ways (absorbed, reflected, refracted, scattered, transtormed into thermal energy) by the atoms, not only by the electrons.

Opaque objects absorb almost all frequencies of the visible spectrum because most frequencies (even those that do not correspond to a specific energy level) are absorbed and transformed into thermal radiation

Some frequencies are scattered, reflected and one ore more frequencies are re-emitted, and that is why opaque object are visible and have colour(s)

... frequencies get absorbed and you basically don't have any visible light coming out on the other end.

In tranparent materials the energy gap between the ground and excited level of a free electron is too high compared to the energy of the photon, which therefore cannot excite the electrons and consequently lose energy. That is why UVA rays pass through a glass and more energetic UVB are blocked.

Light can pass through a body only when photons are absorbed by the inter atomic bonds and re-emitted, this is why why the speed of light is slower in tranparent materials. They are transparent because the direction of the light is preserved by the ordered bonds and because very little energy is lost. In opaque objects photons are emitted or scattered in all directions

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I'm afraid you miss the point that the photon whose frequency does not correspond to a specific energy level difference, cannot be fully absorbed and can only be scattered/reflected with possible energy loss. So the absorption spectrum would not be continuous. –  firtree Aug 25 at 10:43

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