91影视

Radiant energy or also usually called luminosity and is defined as the total energy radiated by the sun per unit time. The units of luminosity are W or J/s.

Intensity or also called radiation flux is defined as the energy flowing through per unit time per unit area.The unit is${W/m}^2$. The radiant fluxF of a star, is related to its luminosity L as follows:

$F\text{鈥�}=\text{鈥�}\frac{L}{4蟺r^2}$

F is the intensity which is$1.5\text{鈥�}kW/m^2$and the distance r to the earth from sun is$1.5\text{鈥�}脳\text{鈥�}{10}^{11}\text{鈥�}m$, putting the values, we get luminosity L as$4.24\text{鈥�}脳\text{鈥�}{10}^{26}\text{鈥�}W$. It means that every second sun is radiating$4.24\text{鈥�}脳\text{鈥�}{10}^{26}\text{鈥�}J$of energy. By using Einstein鈥檚 mass-energyrelation one can determine the amount of mass in the core of the sun converted into radiative energy per second as follows:

$\begin{array}{c}E\text{鈥�}=\text{鈥�}m{c}^2\\ m\text{鈥�}=\text{鈥�}\raisebox{1ex}{$E$}\!\left/ \!\raisebox{-1ex}{$c^2$}\right.\\ m\text{鈥�}=\text{鈥�}\frac{4.24\text{鈥�}脳\text{鈥�}{10}^{26}\text{鈥�}\mathrm{J}\text{鈥�}}{(3\text{鈥�}脳\text{鈥�}{10}^8\text{鈥�}\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s^2$}\right.)}\\ =\text{鈥�}4.7\text{鈥�}脳\text{鈥�}{10}^{9\text{鈥�}}\text{鈥�}kg\end{array}$

Therefore, 4.7 million tons of mass is being converted into this radiant energy every second in the sun鈥檚 core.