The energy flux of the sunlight reaching the surface of the earth is `1.388xx10^(3) W m^(-2)`. How many photons (nearly) per square meter are incident on the earth per second? Assume that the photonsin the sunlight have an average wavelength of 550 nm.

Explanation

Given , energy flux , `P=1.388xx10^3W//m^2`
`:.` Wavelength , `lamda=550 nm =550xx10^(-9)m`
`:.` Number of photons per square metrre incident per second is
`N=P/E=P/(hc//lamda)=(plamda)/(hc)`
`=(1.388xx10^3xx550xx10^(-9))/(6.63xx10^(-34)xx3xx10^8)`
`4xx10^(21)` photons/ `m^2` s