The Radiative Zone!


The core of the Sun is the furnace that creates the energy that powers the Sun. Surrounding the core is the radiative zone where the electromagnetic radiation given off by the core dominates everything else. Since this bit of the Sun is dominated by radiation it is called the radiative zone.



Electromagnetic radiation is all around us at all times - it's basically just a more general name for what we know as light. Every colour you see is just electromagnetic radiation of a different wavelength.

A spectrum


Visible light photons are so called because we can see them (obvious, really)! But there are other photons you can't see with the human eye, like radio, microwaves, infrared, ultraviolet, X-rays and gamma rays.



There is only one difference between all the above types of photon and that is energy. You can think of electromagnetic radiation as being a wave that carries electromagnetic energy. (If you think about it, water waves carry energy too - next time you're at a beach just feel the water slap against your legs or watch the sand move up and down the beach - it takes energy to do that!) Since photons carry energy then electromagnetic radiation is simply a means of transporting energy.

Since it is a wave it has a frequency f and the energy E carried by this wave is

E=hf


where h is called Planck's constant (and that's his picture on the right!)


The electromagnetic waves below all have different energies since they all have different frequencies. The less energetic waves are towards the left and the more energetic waves are on the right.

Right arrow
TV & radio waves Microwaves Infrared Visible Light Ultraviolet X-Rays Gamma Rays

increasing frequency leads to increasing energy




In the radiative zone, the high energy photons produced by the core interact with the particles there - they are absorbed and emitted many times. The effect of all these absorptions and re-emissions is to increase the typical wavelength (or, decrease its frequency), from high energy gamma rays (as generated in the core) to visible light at the solar surface.

There are so many absorptions and re-emissions that it in fact takes around 170,000 years for a photon to reach the solar surface from the core!




But all that energy doesn't just stay in the radiative zone - it has to go somewhere....



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