- #1
iamconfused
- 9
- 1
I'm confused on how something can absorb visible light and release heat. Specifically, I'm confused how the Earth absorbs visible light and emits IR + heat. I'm in a class (about global warming) for non-science majors and don't have much of a background in science, so I would appreciate responses similar to an "explain like I'm 5" response. Here is what I have come to learn so far so you can see where I might be getting lost...
1) The temperature of an object is related to how much the atoms are moving around (kinetic energy). Atoms and molecules in things that are hotter move around more than in things that are colder.
2) There are three ways of transferring heat. Conduction, convection, and radiation. For now I'm going to ignore convection. Conduction, which is like when a hot object with atoms moving around a lot bumps into a cold object and makes the atoms/molecules in the colder object move around more, similar to how slow bumper cars will move faster if fast bumper cars bump into them. Radiation is electromagnetic waves...
3) electromagnetic waves can be absorbed either electronically, vibrationally, rotationally, or translationally (and for the purpose of my question and my sanity, I'm going to ignore rotational and translational). So just looking at electronically and vibrationally...
4) Molecules can absorb radiation vibrationally if there is a dipole when the molecule is vibrating, and if the vibration is "oscillating the electric field around it" at the same frequency as the radiation. This is usually infrared radiation that can make a vibrational transition. When this radiation is absorbed, this makes the molecule vibrate more, and if there are other molecules nearby, it will bump into them and make them move more, which means heat was transferred (because the light went into make things vibrate more).
5) Molecules/atoms can also absorb radiation electronically, which means that an electron will jump up to a higher excited state (if the atom/molecule has a transition at the exact wavelength/frequency as the light that was being absorbed). This is usually UV or Visible light that can make an electronic transition.
So here is where I'm getting lost... The Earth apparently absorbs visible light and gives off heat + IR. I don't understand why an object wouldn't absorb visible light and not just release visible light.
As an example, when I'm shown an energy diagram in class for electronic transitions, I'm assuming that if an electron jumps to n=1 to n=4, then it will just emit light when it goes from n=4 back to n=1. I don't know if this is true, but if it absorbs from n=1 to n=4, could it come back down by releasing a photon from n=4 to n=3? and then n=3 to n=2? etc? This is the only way I could think that something could absorb visible and release IR (less energetic light than what came in). And if this is what is happening, why? Why wouldn't the Earth absorb visible light and give off visible light instead?
And then where does heat come from? How does absorbing visible light electronically make the atoms in a substance move around more?
1) The temperature of an object is related to how much the atoms are moving around (kinetic energy). Atoms and molecules in things that are hotter move around more than in things that are colder.
2) There are three ways of transferring heat. Conduction, convection, and radiation. For now I'm going to ignore convection. Conduction, which is like when a hot object with atoms moving around a lot bumps into a cold object and makes the atoms/molecules in the colder object move around more, similar to how slow bumper cars will move faster if fast bumper cars bump into them. Radiation is electromagnetic waves...
3) electromagnetic waves can be absorbed either electronically, vibrationally, rotationally, or translationally (and for the purpose of my question and my sanity, I'm going to ignore rotational and translational). So just looking at electronically and vibrationally...
4) Molecules can absorb radiation vibrationally if there is a dipole when the molecule is vibrating, and if the vibration is "oscillating the electric field around it" at the same frequency as the radiation. This is usually infrared radiation that can make a vibrational transition. When this radiation is absorbed, this makes the molecule vibrate more, and if there are other molecules nearby, it will bump into them and make them move more, which means heat was transferred (because the light went into make things vibrate more).
5) Molecules/atoms can also absorb radiation electronically, which means that an electron will jump up to a higher excited state (if the atom/molecule has a transition at the exact wavelength/frequency as the light that was being absorbed). This is usually UV or Visible light that can make an electronic transition.
So here is where I'm getting lost... The Earth apparently absorbs visible light and gives off heat + IR. I don't understand why an object wouldn't absorb visible light and not just release visible light.
As an example, when I'm shown an energy diagram in class for electronic transitions, I'm assuming that if an electron jumps to n=1 to n=4, then it will just emit light when it goes from n=4 back to n=1. I don't know if this is true, but if it absorbs from n=1 to n=4, could it come back down by releasing a photon from n=4 to n=3? and then n=3 to n=2? etc? This is the only way I could think that something could absorb visible and release IR (less energetic light than what came in). And if this is what is happening, why? Why wouldn't the Earth absorb visible light and give off visible light instead?
And then where does heat come from? How does absorbing visible light electronically make the atoms in a substance move around more?