h26
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Could someone please help me understand this? I actually thought 3 is the only correct one but apparently the answer is B
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h26
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username3249896
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1 is true

2 is true

3 is false as the radiation absorbed is infra-red not ultraviolet.
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h26
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(Original post by BobbJo)
1 is true

2 is true

3 is false as the radiation absorbed is infra-red not ultraviolet.
Hi thanks a lot for replying . The reason why I am confused here: is what is the solar energy they are referring to here? The uv light from the sun?
Also, for this question below, The answer is d but why isn't C correct? so I thought c isn't correct because c02 molecules absorb uv and radiate IR.
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However, the new question (in my initial post) is saying that greenhouse gases absorb UV so they are sort of contradicting each other.
Could you please lemme know what you think?
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charco
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(Original post by h26)
Hi thanks a lot for replying . The reason why I am confused here: is what is the solar energy they are referring to here? The uv light from the sun?
Also, for this question below, The answer is d but why isn't C correct? so I thought c isn't correct because c02 molecules absorb uv and radiate IR.
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However, the new question (in my initial post) is saying that greenhouse gases absorb UV so they are sort of contradicting each other.
Could you please lemme know what you think?
All radiation from the sun warms up the earth.
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h26
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(Original post by charco)
All radiation from the sun warms up the earth.
thanks but Why is c wrong though?
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(Original post by h26)
Hi thanks a lot for replying . The reason why I am confused here: is what is the solar energy they are referring to here? The uv light from the sun?
Also, for this question below, The answer is d but why isn't C correct? so I thought c isn't correct because c02 molecules absorb uv and radiate IR.
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However, the new question (in my initial post) is saying that greenhouse gases absorb UV so they are sort of contradicting each other.
Could you please lemme know what you think?
Solar energy is the heat and light energy from the sun (from the electromagnetic waves it emits)

CO2 is a simple linear molecule

https://scied.ucar.edu/carbon-dioxid...ared-radiation

The CO2 vibrates temporarily, creating a temporary dipole moment. The absorption of IR radiation is due to vibrations of molecules. When a vibration causes change in charge distribution (or dipole moment to be more specific) the IR radiation is absorbed. Greenhouse gases trap heat, which is predominantly IR radiation.
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h26
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(Original post by BobbJo)
Solar energy is the heat and light energy from the sun (from the electromagnetic waves it emits)

CO2 is a simple linear molecule

https://scied.ucar.edu/carbon-dioxid...ared-radiation

The CO2 vibrates temporarily, creating a temporary dipole moment. The absorption of IR radiation is due to vibrations of molecules. When a vibration causes change in charge distribution (or dipole moment to be more specific) the IR radiation is absorbed. Greenhouse gases trap heat, which is predominantly IR radiation.
Thanks but (sorry going a bit off topic) when light is absorbed by a substance, this causes electrons do be excited to higher energy levels.
In the case of the CO2 molecule, the co2 is always vibrating but then when it absorbs uv light which has been emitted by the sun (ik wrong but anyway to expplain my point), then electrons in the co2 are excited to a higher energy level, when these elelctrons come back down, IR is emitted by the CO2. This ir that the c02 has emitted warms up other air molecules , which then have electrons in them excited and they in turn release ir which warms up the earth.

I incorrectly mentioned what happens to uv from the sun so hat actually happens to the UV from the sun?
also idk where the earth is involved and is it the earth or the atmosphere/troposphere/stratosphere - ik i sound rlly silly

Thanks for sending the link btw -didlook at it
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uberteknik
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(Original post by h26)
Thanks but (sorry going a bit off topic) when light is absorbed by a substance, this causes electrons do be excited to higher energy levels.
In the case of the CO2 molecule, the co2 is always vibrating but then when it absorbs uv light which has been emitted by the sun (ik wrong but anyway to expplain my point), then electrons in the co2 are excited to a higher energy level, when these elelctrons come back down, IR is emitted by the CO2. This ir that the c02 has emitted warms up other air molecules , which then have electrons in them excited and they in turn release ir which warms up the earth.

I incorrectly mentioned what happens to uv from the sun so hat actually happens to the UV from the sun?
also idk where the earth is involved and is it the earth or the atmosphere/troposphere/stratosphere - ik i sound rlly silly

Thanks for sending the link btw -didlook at it
UV is not absorbed by the CO2, it is absorbed by the earth's land surface and sea which then re-radiates as infra-red.

The CO2 absorbs the outgoing infra-red and the energy is redistributed to the atmosphere.

Think about how UV passes through double glazing to heat solid surfaces in a room, but the glass prevents heat loss because infra-red is trapped inside the room.
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h26
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(Original post by uberteknik)
UV is not absorbed by the CO2, it is absorbed by the earth's land surface and sea which then re-radiates as infra-red.

The CO2 absorbs the outgoing infra-red and the energy is redistributed to the atmosphere.

Think about how UV passes through double glazing to heat solid surfaces in a room, but the glass prevents heat loss because infra-red is trapped inside the room.
Thanks a lot was wondering why is B and C wrong here?
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uberteknik
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(Original post by h26)
Thanks a lot was wondering why is B and C wrong here?
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B is incorrect because it describes CO2 as a 'thin blanket' around the earth. CO2 is present throughout the atmosphere.

C is incorrect because the main mechanism for energy absorption of infra-red by CO2 is through increased vibrational modes as BobbJo described previously.
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h26
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(Original post by uberteknik)
B is incorrect because it describes CO2 as a 'thin blanket' around the earth. CO2 is present throughout the atmosphere.

C is incorrect because the main mechanism for energy absorption of infra-red by CO2 is through increased vibrational modes.
Ah thanks a lot! Was wondering what is the difference between vibrational energy and rotational energy -always confuse them
Also, i thought it was the other way round - absorbing ir increases the vibrational energy of the C02 and not vibrational energy of CO2 results in IR absorption
Could you please lemme know your thoughts
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h26
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(Original post by uberteknik)
B is incorrect because it describes CO2 as a 'thin blanket' around the earth. CO2 is present throughout the atmosphere.

C is incorrect because the main mechanism for energy absorption of infra-red by CO2 is through increased vibrational modes as BobbJo described previously.
Ah thanks a lot! Was wondering what is the difference between vibrational energy and rotational energy -always confuse them EDIT: so I sort of get vibrational energy but then what is rotational energy?
Also, i thought it was the other way round - absorbing ir increases the vibrational energy of the C02 and not vibrational energy of CO2 results in IR absorption
EDIT: It's like saying the electrons are excited and then light is absorbed instead of light is absorbed which results in electron excitation - just expanded from my point from before
Could you please lemme know your thoughtsImage
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uberteknik
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(Original post by h26)
Ah thanks a lot! Was wondering what is the difference between vibrational energy and rotational energy -always confuse them
Rotation can be thought of as the molecule spinning on an axis. Energy absorption may cause an increased dipole moment.


(Original post by h26)
Also, i thought it was the other way round - absorbing ir increases the vibrational energy of the C02 and not vibrational energy of CO2 results in IR absorption
Exactly. The infra-red photon absorption causes an increase in the vibrational energy of the CO2 molecules. i.e. as I previously described as increased vibrational modes: energy stored as increased stretching, rocking, twisting, bending etc.
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charco
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(Original post by h26)
Ah thanks a lot! Was wondering what is the difference between vibrational energy and rotational energy -always confuse them
Also, i thought it was the other way round - absorbing ir increases the vibrational energy of the C02 and not vibrational energy of CO2 results in IR absorption
Could you please lemme know your thoughts
Rotational energy levels are changed by microwave radiation (hence microwave ovens).

They are literally changes in the rotational speed of the polar molecules.

Infrared energy affects the stretching and bending of the bonds in the molecules. There are three types: symmetrical stretch, asymmetric stretch and bending (wagging). Only those stretches or bends that change the dipole moment of the molecule are absorptive.

These interactive animations may help:

Vibrational modes
Rotational modes
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h26
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(Original post by uberteknik)
Rotation can be thought of as the molecule spinning on an axis. Energy absorption may cause an increased dipole moment.
Exactly. The infra-red photon absorption causes an increase in the vibrational energy of the CO2 molecules. i.e. as I previously described as increased vibrational modes: energy stored as increased stretching, rocking, twisting, bending etc.
Ah thanks a lot! I am actually getting this
For this one below: The answer is C (2 and 3 only)
1: so energy is never transferred from the sun to the greenhouse molecules and then the earth? Is it because the sun mainly emits uv radiation and since greenhouse gas molecules don't absorb UV this sequence doesn't work?
2: so earth emits IR (cause it absorbed UV from sun) which is absorbed by greenhouse gas molecules and then these greenhouse gas molecules increase in vibrational energy, and so emit IR in the process, and then the IR is reabsorbed by the earth,right?
3: so greenhouse gas molecules emit ir which is absorbed by other air molecules and these air molecules emit ir, right?
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Could you please kindly lemme know your thoughts Will be so much appreciated
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h26
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(Original post by charco)
Rotational energy levels are changed by microwave radiation (hence microwave ovens).

They are literally changes in the rotational speed of the polar molecules.

Infrared energy affects the stretching and bending of the bonds in the molecules. There are three types: symmetrical stretch, asymmetric stretch and bending (wagging). Only those stretches or bends that change the dipole moment of the molecule are absorptive.

These interactive animations may help:

Vibrational modes
Rotational modes
Thank you so much -animations really helped
For this one below: The answer is C (2 and 3 only)
1: so energy is never transferred from the sun to the greenhouse molecules and then the earth? Is it because the sun mainly emits uv radiation and since greenhouse gas molecules don't absorb UV this sequence doesn't work?
2: so earth emits IR (cause it absorbed UV from sun) which is absorbed by greenhouse gas molecules and then these greenhouse gas molecules increase in vibrational energy, and so emit IR in the process, and then the IR is reabsorbed by the earth,right?
3: so greenhouse gas molecules emit ir which is absorbed by other air molecules and these air molecules emit ir, right?
Image
Could you please kindly lemme know your thoughtsImageImage Will be so much appreciated
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charco
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(Original post by h26)
Thank you so much -animations really helped
For this one below: The answer is C (2 and 3 only)
1: so energy is never transferred from the sun to the greenhouse molecules and then the earth? Is it because the sun mainly emits uv radiation and since greenhouse gas molecules don't absorb UV this sequence doesn't work?
2: so earth emits IR (cause it absorbed UV from sun) which is absorbed by greenhouse gas molecules and then these greenhouse gas molecules increase in vibrational energy, and so emit IR in the process, and then the IR is reabsorbed by the earth,right?
3: so greenhouse gas molecules emit ir which is absorbed by other air molecules and these air molecules emit ir, right?
Image
Could you please kindly lemme know your thoughtsImageImage Will be so much appreciated
You've pretty much got the idea ...
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