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. `4 xx 10 ^(21)`
B. `4 xx 10 ^(34)`
C. `4 xx 10 ^(31)`
D. `4 xx 10 ^(28)`

Answer

A

Explanation

Here, `I = 1. 388 xx 10 ^(3) W m ^(-2)`
`lamda = 550 xx 10 ^(-9) m, h = 6.63xx 10 ^( - 34)Js `
The number of photon incident on the earth.s surface per second per square meter is :
`n = (I)/(E) = (I lamda )/( hc) ( because E = (hc)/(lamda ))`
`= ( 1. 388 xx 10 ^(3) xx 550 xx 10 ^(-9))/( 6.63 xx 10 ^(-34) xx 3 xx 10 ^(8)) = 4 xx 10 ^(21).`