Energy from the sun is received on the earth at the rate of `9J//cm^(2)//`minute. The average wavelength of solar light is taken as 5500 Å. How many photons are received on the earth per `cm^(2)` per minute? `[h=6.6xx10^(-34)J-s]`

Options

A. `2.2xx10^(17)`
B. `1.8xx10^(19)`
C. `2.5xx10^(19)`
D. `1.5xx10^(18)`

Answer

C

Explanation

Energy of one photon in the sunlight is
`E=(hC)/(lambda)=(6.6xx10^(-34)xx3xx10^(8))/(5500xx10^(-10))`
`=0.36xx10^(-18)=3.6xx10^(-19)J`
`:.` Number of photons (N) reaching the earth/`cm^(2)`/min
`=("Energy received from the sun")/("Energy of one photon")`
`=(9J)/(3.6xx10^(-19)J)=2.5xx10^(19)`