Blackbody Radiation (Aram Hacobian)
Title: Blackbody Radiation or why you should wear white when it's hot.
*Tape
*Scissors
*2 identical balloons
*2 identical bottles
*Black and white construction paper
Procedure:
1. Obtain materials
2. Tape black and white paper to the outside of the bottles so that they should cover as much of the bottle as possible.
3. Put balloons over opening of bottles to ensure bottles are airtight.
3.5 (optional) Use tape or rubber bands to secure balloons to bottle mouths.
4. Place in a location that gets constant light
5. Be amazed.
Student prior knowledge: Students should know that gases expand when heat up and that heat is transferred through radiation among other ways.
Explanation: Black materials absorbs all wavelengths of light (including IR) and emits IR radiation which we feel as heat very efficiently. White reflects those same wavelengths. Over time, as the bottle wrapped in black emits IR radiation, it causes the air inside the bottle to heat up faster than the bottle wrapped in white. The air expands and goes into the balloon, thus causing it to inflate.
Questions & Answers:
1. How could I use this in my daily life?
Answers will vary but acceptable answer may include wearing white clothing on hot days, getting a white car if you live in a hot area or a black car if you live in a cold area.
2. What are some interesting factors to change in this experiment that may affect the outcome?
Answers will vary but acceptable answers may include changing the color(s) of the paper covering the bottles, changing the materials used on the bottles (say a black & white cloth instead of paper), replace bottles with aluminum soda cans, etc.
3. Why is my white car hot when I leave it outside for an extended period of time?
It's hot since the glass traps the heat that does make it into the car. Since there's no outlet for the heat, it builds up. A white car by itself will not cool the car down.
Applications to Everyday Life:
1. Most airplanes are white since reflecting incoming IR radiation helps cool down the plane.
2. Most people in the Middle East wear white overalls since it helps cool them down.
3. The space shuttle utilizes both colors. White on the top to help reflect sunlight and black on the bottom helps shed the heat of reentry quicker. It's going to get very hot at the bottom anyway.
Photographs: Include photos and diagrams that illustrate the how the investigation is performed.
DO upload photos into the album linked in the left sidebar.
First:
Then add the next 2:
Then you get this: