$12\mathrm{.}24$ Application: Attenuation in the Atmosphere. Measurements with satellites show that the average solar radiation $($solar constant$)$ in space is approximately $1,400\frac{W}{m^2}.$ The total radiation reaching the surface of the Earth on a summer day is approximately $1,100\frac{W}{m^2}\mathrm{.}50\%$ of this radiation is in the visible range. To get some insight into the radiation process, assume an atmosphere which is $15$ km thick. From this calculate the average attenuation constant in the atmosphere over the visible range assuming it is constant throughout the range and that attenuation is the only loss process.