The energy flux of sunlight reaching the surface of the earth is $1.388 \times 10^{3} \;W / m ^{2} .$ 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 $550\;nm$
The energy flux of sunlight reaching the surface of the earth is $1.388 \times 10^{3} \;W / m ^{2} .$ 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 $550\;nm$
Energy flux $=1388\, W / m^2$
wavelength $=550\, nm$
Energy of photon $=h c / \lambda$ $=3.61 \times 10^{-19} \,J$
So no. of photons $= P / E$
$=4 \times 10^{21}\; Photons / m^{2}\; s$
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