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

Options

A. `4xx10^(21)`
B. `4xx10^(34)`
C. `4xx10^(31)`
D. `4xx10^(28)`

Answer

A

Explanation

(a) : Here, `I=3.88xx10^(3)Wm^(-2)`
`lamda=550xx10^(-9)m,h=6.63xx10^(-34)J` s
Number of photons incident on earth's surface per second per square metre is
`n=(I)/(E)=(Ilamda)/(hc)" "( :. E=(hc)/(lamda))`
`=(1.388xx10^(3)xx550xx10^(-9))/(6.63xx10^(-34)xx3xx10^(8))=4xx10^(21)`