Re: Is it true we give out radiation?

Hi Chloe,

Oh yes, odours are not the only thing we emit

Electromagnetic waves include: visible light, which we can see; infrared, which we can sense as heat; ultraviolet, which causes cancer; and x-rays, gamma rays, etc., etc.....

Now there are two important laws of physics pertaining to radiation which will help you answer your questions:

Wien displacement law

l_max = 2897 / T

l_max is the wavelength of maximum emission and T is the temperature in Kelvin.

Now the temperature of the human body is about 310 Kelvin and if you feed that into the above equation you will find that l_max is 9 micrometres (9x10 ^-6 metres). If you look on the following chart of the electomagnet ic spectrum, you will see that the wavelength of maximum emission is in the near infra-red spectrum, which we perceive in the form of heat. Snuggling up to someone will keep you warm and cosy because they are emitting heat!.

The other law which is of use is the

Stefan-Boltzmann Law

E* = sT⁴

where E* = the blackbody irradiance [in W m^-2]
s = 5.67x10^-8 W m^-2 K^-4 (Stefan-Boltzmann constant)
T = the temperature of the radiating body [in degrees K]

This law enables you to calculate how much radiation anybody emits just by knowing their temperature. If the person you are snuggling up to is getting hotter, then they will emit more radiation. If you feed in body temperature into the above equation, you find that a human being emits about 510 Watts per metre².

I cannot answer specifically answer your question about the radiation given off by a nuclear reactor or the amount absorbed by the human body when the sun is shining. Hopefully, a nuclear reactor will be very well insulated and will not radiate too much heat or any other kind of radiation. The radiation flux of the sun is about 1300 Watts per metre². Some of this is reflected, but a large quantity is absorbed. We do absorb all the uv radiation that gets through the atmosphere and that is a major environmental concern as you are probably aware.

The amount of radiation human beings emit depends only on the temperature of our own bodies. It does not matter whether it is day or night. The time of day will only affect how much radiation we reflect.

I hope this answers your question.

Richard Kingsley