How Much More Infrared Does a Sick Individual Emit Compared to a Healthy One?

[MSmith19]

In order to detect SARS, airport officials would use infrared cameras to find potential carriers. A healthy individual would be detected to emit 100microwatts at 37C body temperature, what would a sick individual at 40C body temperature emit? With this answer, what is the difference in emission of a sick individual and a healthy one?

Homework Equations

Radiation out = (5.67*10^-8)(e)(A)(T)^4

Where e ~ 1.

The Attempt at a Solution

0.0001W = (5.67*10^-8)(1)(A)(37)^4

A = 0.000941044249m^2

X W = (5.67*10^-8)(1)(0.000941044249)(40)^4

X W = 0.000136594455

0.000136594455-0.0001 = 0.00003659W = 36.59 microwatts

However, this is apparently the wrong answer. Am I going at the problem in a completely wrong direction?

Thanks a lot for any help.

 

[LowlyPion]

Welcome to PF.

For one thing the Stephan-Boltzmann equation implies the use of degrees °K not °C.

So your temps should be 310° and 313°K

All other things being equal then

X/100 = (313)⁴/(310)⁴

should yield an answer in microwatts shouldn't it?

 

[MSmith19]

Wow that was stupid. Thank you very much for the correction..yes that produces a correct answer.

 

[LowlyPion]

Easy to overlook.

Yet amazingly think how smart nature is to get it right every time.

Cheers.