The sun gives light at the rate of `1400Wm^(-2)` of area perpendicular to the direction of light. Assume `lamda(sunlight)=6000A`. Calculate
A.the number of photons per second arriving at `1 m^2` area at earth.
B. the number of photons emitted from the sun per second assuming the average radius of the Earth's orbit is `1.49xx10^(11)` m.

Explanation

`I=1400Wm^(-2) ` , `lamda=6000A`
A. Energy of the photon, `E=hv=(hc)/(lamda)(c=3xx10^(8)ms^(-1))`
Let N be the number of photons reveived per second per unit area.
`:'` `n=(IA)/(E)=((1400xx1)xx(6000xx10^(-10)))/(6.63xx10^(-34)xx3xx10^(8))`
`=4.22xx10^(21)`
B. Total energy emitted per second `=power(W)` Number of photons emitted form the sun per second,
`n=("Power of sun"(W))/("Energy of a photon")`
`=(Ixx(4piR^(2))xx(6000xx10^(-10)))/(6.63xx10^(-34)xx3xx10^(8))`
`=1.178xx10^(45)`