Stefan-Boltzmann sigma (help urgently needed)

[deleted-523241]

Hello! I was wondering if someone could help me with some questions/problems I have been having with my science fair project (Absorption of Radiant Energy by Different Colors). I have gathered my data, but when I tried to plug the data into one of the Stefan-Boltzmann equation, (namely, P = σ A(T^4 - Ts^4), I got confused. Everything but the sigma makes sense. (The sigma is 5.67 × 10-8 W/m^2 K^4). I don't know what the variables stand for in this sigma, how they cancel out, or if I should replace them with my data. Please help - I don't have much time; my results paper is due tomorrow. Also, if you could check out my project on ScienceBuddies project ideas, and further explain how all the equations work, that would be great.
Thanks,

-Toby

[norman40]

Hi Toby,

I'm assuming that you're working on the project described here:

https://www.sciencebuddies.org/science- ... ion-colors

The symbols shown for the Stefan-Boltzmann constant (sigma) are the units for power (Watts or W), area (square meters or m^2) and Kelvin temperature (raised to the 4th power or K^4). When you complete the multiplications indicated in equation 2 (Background section) the area and temperature units for sigma cancel and you're left with watts for the power.

Just plug the area of your colored paper square (in square meters) and your measured temperatures (in Kelvin) into equation 2. Equation 3 is an example of how to plug in the values.

Equations 4 and 5 are used to estimate the number of photons represented by the power emission.
Plug your power value (from equation 2) into equation 5. Your power value goes into the first term on the left side of equation 5 (replace the 0.92 value with your result from equation 2).

Some additional background information on the Stefan-Boltzmann law is available at the following link.

http://hyperphysics.phy-astr.gsu.edu/hb ... tefan.html

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

A. Norman