# How much of the electromagnetic spectrum does Sun emits?

I'm wondering how much of the electromagnetic spectrum does the sun emits! It obviously emits visible light, but what about the other?
Does the sun emits radio waves? If that's the case why them do not interact with the radio waves on earth?

• Jun 23, 2017 at 17:14
• – user122423
Jun 23, 2017 at 17:33

The Sun is often approximated as a "blackbody". A blackbody whose surface is of temperature $T$ on the Kelvin scale emits radiation of angular frequency $\omega$ with an intensity proportional to $\dfrac{x^3}{e^x-1}$ with $x:=\dfrac{\hbar\omega}{k_B T}$, where $\hbar$ is the Dirac constant and $k_B$ is the Boltzmann constant. This intensity measure is by power; by photon count, we drop one power of $x$. If you work in terms of wavelength, $x=\dfrac{2\pi\hbar c}{k_BT\lambda}$.
On this model, any frequency can be emitted to some extent, so you have to decide what's a non-negligible emission. (For example, is an intensity $1,000$ times less than the peak negligible?) Animal eyes evolved to exploit sunlight for vision, and both infrared and ultraviolet (which are slightly outside human vision) are a large enough part of the Sun's output for some animals to use it. However, radio waves (which have much lower frequencies than infrared) are essentially absent, as are X-rays (which have much higher frequencies than ultraviolet).