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The energy flux of sunlight reaching the surface of the earth is 1.388xx10^(3)W//m^(-2). How many photons (nearly) perr square metre are incident on the earth per second ? Assume that the photons in the sunlight have an average wavelength of 550 nm. |
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Answer» Solution :Here ENERGY of flux of photons per UNIT area `phi=1.388xx10^(3)Wm^(-2)`, and wavelength of sunlight `lamda=550nm=5.5xx10^(-7)m` `THEREFORE`Energy of each photon `E=(hc)/(lamda)=(6.63xx10^(-34)xx3xx10^(8))/(5.5xx10^(-7))=3.6xx10^(-19)J` `therefore`Number of photons incident per square metre on earth per second `n=(phi)/(E)=(1.388xx10^(3))/(3.6xx10^(-19))=4XX10^(21)m^(-2)s^(-1)`. |
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