The energy flux of sunlight reaching the surface of the earth is 1.388 10^3 ~W ~m ⁻² . How many photons (nearly) per square metre are incident on the earth per second? Assume that the photons in the sunlight have an average wavelength of 550 ~nm .

Step-by-step solution

Energy flux = Energy of photons from reaching the earth per second per unit area =1.388 10^3 ~W ~m ⁻²=1.388 10^3 ~J ~s ⁻¹ ~m ⁻² Let n= number of photons incident on earth per m ⁻² and E^ = energy of each photon = h c If E be the energy of all photons reaching the surface of earth per sec per unit area, then aligned & E=n E^ = n h c & n h c = or n= ( h c ) = 1.388 10^3 h c aligned = 1.388 10^3 550 10⁻⁹ 6.62 10⁻³⁴ 3 10^8 =3.85 10²¹