Color Absorption Help!

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Stareo
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Color Absorption Help!

Post by Stareo »

I'm doing the Infrared Absorption project, where you place colored construction paper squares in direct sunlight, take their temperatures, and use the Stefan Boltzmann equation to calculate the infrared re-emission levels. I've procrastinated a little :oops: and my project is due very soon. In my area the weather is really cold, and I'm hoping it won't affect the outcome too much! Also, I don't have a thermometer, only the infrared thermometer to check the temperatures of the squares. So, is it OK if I use the weather.com temperature, and if so, should I use the main temperature or the "feels like" temperature?
And, will the cold, windy weather (like 15 - 20 degrees Fahrenheit) heavily affect my project outcome?
I'm really hoping for fast advice, as my project is due very, very soon!
norman40
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Re: Color Absorption Help!

Post by norman40 »

Hello Stareo,

I’m assuming that you are working on the project described here:

https://www.sciencebuddies.org/science- ... ml#summary

Sorry to hear about your cold weather conditions. But I don’t think that will affect your project results as long as you can find a sunny spot for your colored paper squares. And you should protect the paper squares from the wind. If all the paper squares get equal sun exposure and wind protection you should get similar results regardless of the outdoor temperature.

The infrared thermometer is the only one you need for the project. It measures the energy emitted from the colored paper squares. The air temperature, as reported by online weather sites, is not used in this project. But you could note the outside air temperature during your experiment.

I hope this helps and good luck with your project. Please post again if you have more questions.

A. Norman
Stareo
Posts: 8
Joined: Tue May 31, 2016 1:08 pm
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Re: Color Absorption Help!

Post by Stareo »

norman40 wrote:Hello Stareo,

I’m assuming that you are working on the project described here:

https://www.sciencebuddies.org/science- ... ml#summary

Sorry to hear about your cold weather conditions. But I don’t think that will affect your project results as long as you can find a sunny spot for your colored paper squares. And you should protect the paper squares from the wind. If all the paper squares get equal sun exposure and wind protection you should get similar results regardless of the outdoor temperature.

The infrared thermometer is the only one you need for the project. It measures the energy emitted from the colored paper squares. The air temperature, as reported by online weather sites, is not used in this project. But you could note the outside air temperature during your experiment.

I hope this helps and good luck with your project. Please post again if you have more questions.

Thanks! This helped a lot. But I noticed you said it doesn't require the air temperature, but the project says it does. You need to measure the surrounding temperature in (I believe) equation two. It says P = stefan's constant*area*(temperature to the fourth power - surrounding temperature to the fourth power). Clarification would be helpful.

Also, it's not going to be fully sunny here, so would partially cloudy/sunny work?

A. Norman
Stareo
Posts: 8
Joined: Tue May 31, 2016 1:08 pm
Occupation: Student

Re: Color Absorption Help!

Post by Stareo »

norman40 wrote:Hello Stareo,

I’m assuming that you are working on the project described here:

https://www.sciencebuddies.org/science- ... ml#summary

Sorry to hear about your cold weather conditions. But I don’t think that will affect your project results as long as you can find a sunny spot for your colored paper squares. And you should protect the paper squares from the wind. If all the paper squares get equal sun exposure and wind protection you should get similar results regardless of the outdoor temperature.

The infrared thermometer is the only one you need for the project. It measures the energy emitted from the colored paper squares. The air temperature, as reported by online weather sites, is not used in this project. But you could note the outside air temperature during your experiment.

I hope this helps and good luck with your project. Please post again if you have more questions.

A. Norman
I did my experiment, and I got REALLY inconsistent results! Using construction paper for every color of the rainbow, the only consistent thing was that green always had the highest temperature. What to do? What would consistent results look like and what should be the highest and lowest temperature colors?
norman40
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Re: Color Absorption Help!

Post by norman40 »

Hi Stareo,

The “surrounding” temperature used in equation 2 is measured with the infrared thermometer for a piece of white paper. A square of white construction paper is included in the set of colored paper samples (see step 1 of the experimental procedure). As noted later, the temperature reading from the white paper is used as the surrounding temperature in equation 2 (see step 8 ).

Partly sunny weather might be OK for your experiments. You want to make sure that all of your paper squares are exposed to the same amount of light during your measurements. If the sun is behind a cloud for some of your measurements but shining brightly for others, your results won’t be comparable.

When you say that your results were inconsistent do you mean that you found different temperatures for the various colors of paper? If so, this is the expected result. And part of the objective of this project is to show the range of temperatures and energies emitted by different colors. The background section contains some more information about which colors should have the highest and lowest temperatures.

On the other hand you should not see big differences among repeated temperature readings for the same color paper. Repeated measurements shouldn’t vary by more than a few degrees. If you have this kind of inconsistency it means that there are some variables in your test procedure that need to be controlled or eliminated. For example, if the amount of sunlight changed during repeat testing of a sample, you might expect inconsistent temperature readings. Another example might be variable distance between the thermometer and paper sample. You’ll want to keep the location of the thermometer and paper samples the same during your tests.

I hope this helps. Please post again if you have more questions.

A. Norman
Stareo
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Re: Color Absorption Help!

Post by Stareo »

norman40 wrote:Hi Stareo,

The “surrounding” temperature used in equation 2 is measured with the infrared thermometer for a piece of white paper. A square of white construction paper is included in the set of colored paper samples (see step 1 of the experimental procedure). As noted later, the temperature reading from the white paper is used as the surrounding temperature in equation 2 (see step 8 ).

Partly sunny weather might be OK for your experiments. You want to make sure that all of your paper squares are exposed to the same amount of light during your measurements. If the sun is behind a cloud for some of your measurements but shining brightly for others, your results won’t be comparable.

When you say that your results were inconsistent do you mean that you found different temperatures for the various colors of paper? If so, this is the expected result. And part of the objective of this project is to show the range of temperatures and energies emitted by different colors. The background section contains some more information about which colors should have the highest and lowest temperatures.

On the other hand you should not see big differences among repeated temperature readings for the same color paper. Repeated measurements shouldn’t vary by more than a few degrees. If you have this kind of inconsistency it means that there are some variables in your test procedure that need to be controlled or eliminated. For example, if the amount of sunlight changed during repeat testing of a sample, you might expect inconsistent temperature readings. Another example might be variable distance between the thermometer and paper sample. You’ll want to keep the location of the thermometer and paper samples the same during your tests.

I hope this helps. Please post again if you have more questions.

A. Norman
By inconsistent, I mean that between each of the three trials, some colors changed their spot on the list. The color that had the lowest temperature in the first trial did not come out as lowest in the second trial, and the same occurred for a few others. The temperature readings changed by about a few tenths of a degree to a whole degree each trial, and as I said, some colors changed their spot on the list through the experiment.
norman40
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Re: Color Absorption Help!

Post by norman40 »

Hi Stareo,

From your description it seems that your temperature readings are reasonably repeatable. And the effect of the color is greater than the measurement variability. Do the averages for the repeat trials show clear differences by color? If so your results are as expected. If not you may want to try changing some of your experimental procedures.

The consistency and range of your temperature measurements can be affected by how you use the infrared thermometer. One factor is the distance between the thermometer and your paper sample when making measurements. Another is that the thermometer should be at the temperature of the surroundings for best results. The following link explains some guidelines for using an infrared thermometer that may be helpful in your experiment.

http://en-us.fluke.com/community/fluke- ... meter.html

As you’ve mentioned, you’ve had partly sunny/partly cloudy weather conditions. The colored paper squares need to be even lit by sunlight for a few minutes before and during the temperature measurements. Changes to the amount of light on the samples could affect the range and consistency of your results.

You might consider repeating the experiment with the following procedures included. Be sure to set up the thermometer at a fixed distance from your paper squares. Put the thermometer in position 20 or 30 minutes before you start your tests. Position your paper squares so that they are evenly lit by sunlight for 2 or 3 minute before taking the temperatures.

I hope this helps. Please post again if you have more questions.

A. Norman
Stareo
Posts: 8
Joined: Tue May 31, 2016 1:08 pm
Occupation: Student

Re: Color Absorption Help!

Post by Stareo »

norman40 wrote:Hi Stareo,

From your description it seems that your temperature readings are reasonably repeatable. And the effect of the color is greater than the measurement variability. Do the averages for the repeat trials show clear differences by color? If so your results are as expected. If not you may want to try changing some of your experimental procedures.

The consistency and range of your temperature measurements can be affected by how you use the infrared thermometer. One factor is the distance between the thermometer and your paper sample when making measurements. Another is that the thermometer should be at the temperature of the surroundings for best results. The following link explains some guidelines for using an infrared thermometer that may be helpful in your experiment.

http://en-us.fluke.com/community/fluke- ... meter.html

As you’ve mentioned, you’ve had partly sunny/partly cloudy weather conditions. The colored paper squares need to be even lit by sunlight for a few minutes before and during the temperature measurements. Changes to the amount of light on the samples could affect the range and consistency of your results.

You might consider repeating the experiment with the following procedures included. Be sure to set up the thermometer at a fixed distance from your paper squares. Put the thermometer in position 20 or 30 minutes before you start your tests. Position your paper squares so that they are evenly lit by sunlight for 2 or 3 minute before taking the temperatures.

I hope this helps. Please post again if you have more questions.

A. Norman
Today was a fully sunny day, although about 10 degrees colder. Since you said the surrounding temperature wouldn't matter as much as long as it was sunny, I redid my experiment. The surrounding temperature was 0 degrees Celsius, and my results, in degrees Celsius, were as follows, :
'


Trial 1 Trial 2 Trial 3

Red, 10.1, 10.0, 9.0,
Orange, 8.2, 8.4, 7.9,
Yellow, 6.9, 6.3, 6.0,
Green, 9.7, 10.2, 9.3,
Blue, 9.2, 10.7, 10.3,
Purple, 7.0, 7.2, 7.4,

For a surrounding temperature of zero degrees, do those look about right? And, are the colors that are supposed to be hotter correct and the colors that should be colder end up being colder?
Stareo
Posts: 8
Joined: Tue May 31, 2016 1:08 pm
Occupation: Student

Re: Color Absorption Help!

Post by Stareo »

norman40 wrote:Hi Stareo,

From your description it seems that your temperature readings are reasonably repeatable. And the effect of the color is greater than the measurement variability. Do the averages for the repeat trials show clear differences by color? If so your results are as expected. If not you may want to try changing some of your experimental procedures.

The consistency and range of your temperature measurements can be affected by how you use the infrared thermometer. One factor is the distance between the thermometer and your paper sample when making measurements. Another is that the thermometer should be at the temperature of the surroundings for best results. The following link explains some guidelines for using an infrared thermometer that may be helpful in your experiment.

http://en-us.fluke.com/community/fluke- ... meter.html

As you’ve mentioned, you’ve had partly sunny/partly cloudy weather conditions. The colored paper squares need to be even lit by sunlight for a few minutes before and during the temperature measurements. Changes to the amount of light on the samples could affect the range and consistency of your results.

You might consider repeating the experiment with the following procedures included. Be sure to set up the thermometer at a fixed distance from your paper squares. Put the thermometer in position 20 or 30 minutes before you start your tests. Position your paper squares so that they are evenly lit by sunlight for 2 or 3 minute before taking the temperatures.

I hope this helps. Please post again if you have more questions.

A. Norman
Another question I have is about the act that they tell you to assume the energy of an infrared photon is 0.000124 eV. I've done some research and found that it depends on wavelength, but there's so many types of infrared with so many different wavelengths that there's a bunch of different possible infrared photon energies. For example, one source even says it could be 1.7 eV per photon. That's a lot more than 0.000124 eV per photon! Which one should I use? Help!
norman40
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Re: Color Absorption Help!

Post by norman40 »

Hi Stareo,

I’m glad to hear that you had a sunny day for your experiment.

Your results show very good consistency within repeat trials. The average temperatures for red, green and blue are about the same. But you found lower average temperatures for yellow and purple.

Darker colors should absorb and emit more energy. So higher temperatures would be expected for darker colors. Lower temperatures would be expected for lighter colors due to relatively less absorption and emission of energy. Are your yellow and purple paper samples lighter than the red, green and blue?

Regarding your second question, a range of infrared wavelengths (and photon energies) is emitted. An exact calculation would require measurement of all the emitted wavelengths. To simplify the experiment and calculations, you can use an average value for the photon energy. My suggestion is to use the average value given in the project background section (0.000124 eV/photon).

I hope this helps. Please post again if you have more questions.

A. Norman
Stareo
Posts: 8
Joined: Tue May 31, 2016 1:08 pm
Occupation: Student

Re: Color Absorption Help!

Post by Stareo »

norman40 wrote:Hi Stareo,

I’m glad to hear that you had a sunny day for your experiment.

Your results show very good consistency within repeat trials. The average temperatures for red, green and blue are about the same. But you found lower average temperatures for yellow and purple.

Darker colors should absorb and emit more energy. So higher temperatures would be expected for darker colors. Lower temperatures would be expected for lighter colors due to relatively less absorption and emission of energy. Are your yellow and purple paper samples lighter than the red, green and blue?

Regarding your second question, a range of infrared wavelengths (and photon energies) is emitted. An exact calculation would require measurement of all the emitted wavelengths. To simplify the experiment and calculations, you can use an average value for the photon energy. My suggestion is to use the average value given in the project background section (0.000124 eV/photon).

I hope this helps. Please post again if you have more questions.

A. Norman
Thanks. I used 0.000124 eV as the average infrared photon energy like you said. However, I DID get lower temperatures for yellow and purple. I don't understand how yellow can be HIGHER than anything else, as it is a very light color. However, purple was somewhat dark, definitely darker than the red I used. I'm attaching a copy of my PowerPoint. Scroll to the slide with my graphs, and you'll see the exact results (I averaged the temperatures for the first graph). Is there something wrong with my results? Did I get something different than what was expected?
Attachments

[The extension pptx has been deactivated and can no longer be displayed.]

norman40
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Re: Color Absorption Help!

Post by norman40 »

Hi Stareo,

Based on the descriptions you’ve posted, I don’t think there’s anything wrong with your results. And I think you made the correct conclusion from your results. Nice work!

In this experiment, you would expect lower temperatures for lighter colors. And your temperature data suggest that yellow, purple and orange were lighter than the other colors you tested. But you said that purple was darker than the red sample you tested. If purple was a darker color then its lower temperature doesn’t seem to fit with the light color/lower temperature explanation.

Does the purple sample have shiny surface (more so than the other samples)? A shiny surface could result in more reflected light, less absorbed light and lower temperature.

I hope this helps. Please post again if you have more questions.

A. Norman
Stareo
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Joined: Tue May 31, 2016 1:08 pm
Occupation: Student

Re: Color Absorption Help!

Post by Stareo »

norman40 wrote:Hi Stareo,

Based on the descriptions you’ve posted, I don’t think there’s anything wrong with your results. And I think you made the correct conclusion from your results. Nice work!

In this experiment, you would expect lower temperatures for lighter colors. And your temperature data suggest that yellow, purple and orange were lighter than the other colors you tested. But you said that purple was darker than the red sample you tested. If purple was a darker color then its lower temperature doesn’t seem to fit with the light color/lower temperature explanation.

Does the purple sample have shiny surface (more so than the other samples)? A shiny surface could result in more reflected light, less absorbed light and lower temperature.

I hope this helps. Please post again if you have more questions.

A. Norman
The purple did not have a shiny surface.
However, it could be interpreted as lighter than the red I used, I can't tell by myself. Would you like me to send some photos of the colors I used?
norman40
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Re: Color Absorption Help!

Post by norman40 »

Hi Stareo,

I don’t know of a simple and objective way to rate “lightness” of a color. So trust your judgement. If you think the purple sample is lighter than the red one, it probably is.

I hope this helps. Please post again if you have more questions.

A. Norman
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