Question

what is the approximate value of solar constant

Answer 1

The rate at which energy reaches the earth's surface from the sun, usually taken to be 1,388 watts per square metre.

Answer 2

Solar constant, the total radiationenergyreceived from theSunper unit of time per unit of area on a theoretical surface perpendicular tothe Sun’s rays and atEarth’smean distance from the Sun. It is most accurately measured fromsatelliteswhere atmospheric effects are absent. The value of theconstant is approximately 1.366 kilowatts per square metre. The “constant” is fairly constant, increasing by only 0.2 percent at the peak of each 11-yearsolar cycle.Sunspotsblock out the light and reduce the emission by a few tenths of a percent, but bright spots, called plages, that are associated with solar activity are more extensive and longer lived, sotheir brightness compensates for the darkness of the sunspots. Moreover, as the Sun burns up itshydrogen, the solar constant increases by about 10 percent every billion years.