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How many photons are received on earth per `cm^-2` per hour if the energy from the sun reaching on the earth is at the rate of `2cal cm^(-2) min^(-1)` and average wavelength of solar light be taken as 5500Å. Use `h=6.6xx10^(-34)J , c=3xx10^8ms^(-1)` and `1cal =4,2J` |
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Answer» Here, `lambda=5500Å =5500xx10^(-10)m` Rate of solar energy reaching earth from the sun `=2calcm^-2min^-1=2xx4.2Jcm^-2min^-1` `=2xx4.2xx60Jcm^-2hour^-1` Energy of photon received on earth `E=(hc)/lambda=((6.6xx10^(-34))xx(3xx10^8))/(5500xx10^(-10))` `=3.6xx10^(-19)J` If n number of photons is reaching the earth per `cm^2`per hour, then total energy will be `=nE=nxx3.6xx10^(-19)J cm^-2h^-1` `:. nxx3.6xx10^(-19)=2xx4.2xx60` or `n=(2xx4.2xx60)/(3.6xx10^(-19))=1.4xx10^(21)` |
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