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# Science Question Pertaining to Light

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Consider an object that reflects only the red colors (i.e., 620–750 nm wavelengths) in the visible spectrum. Suppose someone shines a monochromatic blue light on the object. What happens to the light/energy when it hits the object?

As I understand, the light would be absorbed. Since the energy from the light does not correspond with the discreet jumps of the electron energy levels, the object would not reflect the blue light. Intuitively, it doesn't seem reasonable that the object could continually absorb the energy from the photons without increasing the energy levels of the electrons. That would mean that the electron energy levels would eventually fall back down, emitting red photons in the process. So, the result would be shining blue light on an object and seeing that light reflected back as red, which seems very wrong.

So what happens when the blue light is shined on the red object? Does it vary with the intensity of the blue light?
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jcd11235

Consider an object that reflects only the red colors (i.e., 620–750 nm wavelengths) in the visible spectrum. Suppose someone shines a monochromatic blue light on the object. What happens to the light/energy when it hits the object?

As I understand, the light would be absorbed. Since the energy from the light does not correspond with the discreet jumps of the electron energy levels, the object would not reflect the blue light. Intuitively, it doesn't seem reasonable that the object could continually absorb the energy from the photons without increasing the energy levels of the electrons. That would mean that the electron energy levels would eventually fall back down, emitting red photons in the process. So, the result would be shining blue light on an object and seeing that light reflected back as red, which seems very wrong.

So what happens when the blue light is shined on the red object? Does it vary with the intensity of the blue light?

42.
I'm not usually into the whole 3-way thing, but you got me a little excited with that. - Skymama
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jcd11235

Consider an object that reflects only the red colors (i.e., 620–750 nm wavelengths) in the visible spectrum. Suppose someone shines a monochromatic blue light on the object. What happens to the light/energy when it hits the object?

As I understand, the light would be absorbed. Since the energy from the light does not correspond with the discreet jumps of the electron energy levels, the object would not reflect the blue light. Intuitively, it doesn't seem reasonable that the object could continually absorb the energy from the photons without increasing the energy levels of the electrons. That would mean that the electron energy levels would eventually fall back down, emitting red photons in the process. So, the result would be shining blue light on an object and seeing that light reflected back as red, which seems very wrong.

So what happens when the blue light is shined on the red object? Does it vary with the intensity of the blue light?

Sounds like fluorescence to me.

Usually it's UV that illuminates the object, and it re-emits in the visible range (blue/green normally, but not necessarily)
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kallend

***Consider an object that reflects only the red colors (i.e., 620–750 nm wavelengths) in the visible spectrum. Suppose someone shines a monochromatic blue light on the object. What happens to the light/energy when it hits the object?

As I understand, the light would be absorbed. Since the energy from the light does not correspond with the discreet jumps of the electron energy levels, the object would not reflect the blue light. Intuitively, it doesn't seem reasonable that the object could continually absorb the energy from the photons without increasing the energy levels of the electrons. That would mean that the electron energy levels would eventually fall back down, emitting red photons in the process. So, the result would be shining blue light on an object and seeing that light reflected back as red, which seems very wrong.

So what happens when the blue light is shined on the red object? Does it vary with the intensity of the blue light?

Sounds like fluorescence to me.

Usually it's UV that illuminates the object, and it re-emits in the visible range (blue/green normally, but not necessarily)

Thank you. That's very helpful. It does raise more questions, however.

Do most objects fluoresce?

Suppose I shine a broad spectrum white light (let's say a 3200 K correlated color temperature xenon incandescent lamp) at a tree. Since the tree does not reflect all of the component wavelengths of the white light, do the non-reflected wavelengths result in fluorescence?
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Depending upon the object's surface conformations and chemistry, you could see a variety of colors/wavelengths. If an object is not directly emitting or reflecting a particular wavelength, the "color" perceived is based upon the relative amount of scattering among all of the visible wavelengths.

Fluorescence is a little bit different (and rare), in that it is a function of particular molecular conformations (usually conjugated pi bonds / molecular orbitals) which have appropriate characteristics to absorb one wavelength (and thus bump an electron to a higher energy level) and then emit a different wavelength upon relaxation.
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Iago

*********Consider an object that reflects only the red colors (i.e., 620–750 nm wavelengths) in the visible spectrum. Suppose someone shines a monochromatic blue light on the object. What happens to the light/energy when it hits the object?

As I understand, the light would be absorbed. Since the energy from the light does not correspond with the discreet jumps of the electron energy levels, the object would not reflect the blue light. Intuitively, it doesn't seem reasonable that the object could continually absorb the energy from the photons without increasing the energy levels of the electrons. That would mean that the electron energy levels would eventually fall back down, emitting red photons in the process. So, the result would be shining blue light on an object and seeing that light reflected back as red, which seems very wrong.

So what happens when the blue light is shined on the red object? Does it vary with the intensity of the blue light?

Sounds like fluorescence to me.

Usually it's UV that illuminates the object, and it re-emits in the visible range (blue/green normally, but not necessarily)

Thank you. That's very helpful. It does raise more questions, however.

Do most objects fluoresce?

Suppose I shine a broad spectrum white light (let's say a 3200 K correlated color temperature xenon incandescent lamp) at a tree. Since the tree does not reflect all of the component wavelengths of the white light, do the non-reflected wavelengths result in fluorescence?

Most complex organics fluoresce. Waxes, petroleum jelly, etc. There are normally fluorescent compounds in laundry detergent which makes 'the whites whiter and the colors brighter.'

And why your white shirts glow in black light.
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The energy gets absorbed, dosen't reach the level to relase more photons, but does raise the system energy,...

C
But what do I know, "I only have one tandem jump."

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ChrisD

The energy gets absorbed, dosen't reach the level to relase more photons, but does raise the system energy,...

C

I didn't ask anything. Are you sure you're replying to the right person?
...

The only sure way to survive a canopy collision is not to have one.

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Machupo

Depending upon the object's surface conformations and chemistry, you could see a variety of colors/wavelengths. If an object is not directly emitting or reflecting a particular wavelength, the "color" perceived is based upon the relative amount of scattering among all of the visible wavelengths.

I'm not clear on what you mean by scattering in this context. Could you please elaborate some?
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jcd11235

I'm not clear on what you mean by scattering in this context. Could you please elaborate some?

Scattering and diffuse reflection are two pretty closely related terms (IIRC, it depends upon the depth in the material you are investigating... DR is slightly subsurface form of scattering). At any rate, it involves:
- The chemical makeup of the surface, i.e. based upon the bonds between the atoms which make up your (sub)surface. This comes into play when you look at bond energies and the specific energy levels of electrons of the component atoms. Energy that can be absorbed by electrons (in order to excite them to higher energy levels) may do so, otherwise the light will be reflected based upon:

- The physical makeup of the (sub)surface. The shape of the (sub)surface will direct the majority of diffuse reflection (in a sufficiently random surface, omnidirectional reflected light can be considered randomly "scattered") of the light.

On the quantum scale, you're seeing emitted (if it can be absorbed) and reflected (if it cannot) light moving from atom to atom through the surface of the object until one of the reflection probabilities directs it back to your eye (with no other interactions along the way).

Depending on how deep you need to go into the reasoning, there are various theories out there; quantum electrodynamics hurts my head, lol and it gets even weirder when you start looking at nanostructured metamaterials

Caveat: I'm not a physics professor :D
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kallend

***The energy gets absorbed, dosen't reach the level to relase more photons, but does raise the system energy,...

C

I didn't ask anything. Are you sure you're replying to the right person?

I will defiantly admit that my scatter brain frequently confuses and confounds my view of life. I frequently have no idea about the meaning of life or "If I'm replying to the ""right person."""

I much preferre the popular phrase:

"U TalKEN To ME!"

thanks K I know you have a different view on Chemestry (Quantum theory) than the OP...

But it is kind of fun to learn from all of the stereotypes.

C
But what do I know, "I only have one tandem jump."

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Quote

Suppose I shine a broad spectrum white light (let's say a 3200 K correlated color temperature xenon incandescent lamp) at a tree. Since the tree does not reflect all of the component wavelengths of the white light, do the non-reflected wavelengths result in fluorescence?

I would guess the non reflected wavelengths absorb as heat energy and reemit in the infrared spectrum, invisible to us but visible with IR scopes.

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>Intuitively, it doesn't seem reasonable that the object could continually absorb the
>energy from the photons without increasing the energy levels of the electrons.

The key here is that the object continually absorbs the energy - but that energy is turned into heat, not stored energy in electron orbitals.

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billvon

>Intuitively, it doesn't seem reasonable that the object could continually absorb the
>energy from the photons without increasing the energy levels of the electrons.

The key here is that the object continually absorbs the energy - but that energy is turned into heat, not stored energy in electron orbitals.

Yes. The quanta of energy absorbed quickly gets distributed to multiple locations each with a slightly higher energy (such as vibrational and/or rotational states) in the initial molecule and then through collisions to it's neighbors, and then emitted in tiny chunks at very long wavelenths, essentially as black-body radiation.

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Thank you, everyone.
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Divalent

Yes. The quanta of energy absorbed quickly gets distributed to multiple locations each with a slightly higher energy (such as vibrational and/or rotational states) in the initial molecule and then through collisions to it's neighbors, and then emitted in tiny chunks at very long wavelenths, essentially as black-body radiation.

Ooo, like I said, only smarterer.

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I love discussions like this...

My wife is hotter than your wife.

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