Far IR light intensity as a function of altitude

In summary, the conversation is about a project involving building sensors and sending them up in a weather balloon to quantify the greenhouse effect. The goal is to measure the intensity of infrared light emitted from the Earth as the balloon rises, taking into account absorption by water vapor and other greenhouse gases. The student has calculated the change in intensity due to spherical geometry and has a couple of questions about the experiment, including the assumption that far-IR light from the sun is negligible compared to that radiated from the Earth and the concern that light absorbed by water vapor may skew the data. The conversation also mentions the search for a circuit component that can detect light intensity in the 10 μm range.
  • #1
oobgular
8
0

Homework Statement


Hello, so I'm in a class that is building sensors and sending them up in a weather balloon. For my project, I am wanting to quantify the greenhouse effect by measuring the intensity of infrared light emitted as thermal radiation from the Earth as a function of height-- the idea is that as the balloon rises, some of the IR light is absorbed by water vapor and other greenhouse gases, causing intensity to go down.

Homework Equations


From Wein's displacement law, I know emitted radiation will be about 10 μm. I calculated the change in intensity due to spherical geometry causing an increase in area.

The Attempt at a Solution


I have a couple questions about the experiment and one problem.

1. It seems like the intensity of far-IR light from the sun is negligible compared to that radiated from the Earth. Is this a reasonable assumption?

2. I am unable to find data on emission of water vapor. Will the light absorbed be re-emitted at the same wavelength, skewing our data? This is my biggest concern, because it would basically invalidate the experiment.

Finally, we have been searching for a circuit component that detects light intensity in the 10 μm range. Have any of you used one in this range? It must detect intensity of the wavelength.

Thanks you so much!
 
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  • #2
oobgular said:
I calculated the change in intensity due to spherical geometry causing an increase in area.
For the same solid angle, that should cancel with the inverse square law. Without absorption or emission in the air the mean intensity should not change. You just average over a larger area (make sure you measure a homogeneous area).
oobgular said:
1. It seems like the intensity of far-IR light from the sun is negligible compared to that radiated from the Earth. Is this a reasonable assumption?
You can check the emission values and compare them. A sensor that is not in direct sunlight avoids that issue.
oobgular said:
2. I am unable to find data on emission of water vapor. Will the light absorbed be re-emitted at the same wavelength, skewing our data? This is my biggest concern, because it would basically invalidate the experiment.
Infrared will be scattered in the atmosphere, sure, and you have to think how this influences your measurements.
Measurements in different directions could help to distinguish between different infrared sources.
oobgular said:
Finally, we have been searching for a circuit component that detects light intensity in the 10 μm range. Have any of you used one in this range? It must detect intensity of the wavelength.
There are many commercial detectors for this wavelength range. You might have to filter out other wavelength ranges first if the detector doesn't do that.
 

1. What is far infrared light intensity?

Far infrared (FIR) light intensity refers to the amount of electromagnetic radiation with wavelengths between 15 micrometers and 1 millimeter that is present in a specific area or at a specific altitude. It is a type of light that is invisible to the human eye but can be felt as heat.

2. How does far infrared light intensity change with altitude?

As altitude increases, the atmosphere becomes thinner and there is less air to absorb and scatter FIR light. Therefore, the intensity of FIR light increases with altitude because there is less interference from the atmosphere.

3. What factors affect the intensity of far infrared light at different altitudes?

The main factors that affect the intensity of FIR light at different altitudes include the composition and density of the atmosphere, the presence of water vapor, and the amount of solar activity. These factors can vary depending on location and time of day.

4. Can far infrared light be measured at different altitudes?

Yes, far infrared light can be measured at different altitudes using instruments such as spectrometers or radiometers. These devices can detect and measure the intensity of FIR light and provide valuable data for scientific research and atmospheric studies.

5. Why is understanding far infrared light intensity at different altitudes important?

Understanding the changes in FIR light intensity at different altitudes can provide valuable insights into the composition and behavior of the Earth's atmosphere. It can also help in the study of climate change, as FIR light plays a role in the Earth's energy balance and can affect weather patterns and temperature regulation.

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