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.

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6.4: The Compton Effect - Physics LibreTexts
Nov 5, 2020 ... The Compton effect is the term used for an unusual result observed when ... Describe how experiments with X-rays confirm the particle nature of radiation ... Here the photon's energy Ef is the same as that of a light quantum of ... The wave relation that connects frequency f with wavelength λ and speed c ...
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Given that
Energy flux of sunlight P\ =1.388*10^3W/m^2
Average wavelength \lambda = 550 nm = 550 * 10^{-9} m
Step 1: Find the energy of photon in the light beam.
Energy of proton E=h\upsilon\ =\ \frac{hc}{\lambda}
Where, h - Planck's constant (6.626*10^{-34}), speed of light c = 3*10^{8} m/s and \upsilon - frequency
E=\frac{6.626*10^{-34}\cdot3\cdot10^8}{550\cdot10^{-9}\ }
E=3.61\cdot10^{-19}\ J
Step 2: Determining the number of photons per second, on the average
Relation between power(energy flux) and energy of photon
P = nE
Number of photons per second n = \frac{P}{E}
n=\frac{1.388\cdot10^3}{3.62\cdot10^{-19}}
n=3.9\cdot10^{21\ } potons/sec
Hence, Number of photons per square meter o earth per second n=3.9\cdot10^{21\ } potons/sec