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Energy from the sun is recived on earth at the rate of `2` cal per `cm^(2)` per min. If avergae wavelength of solar light be taken at `5500 A` then how many photons are recived on the earth per `cm^(2)` per min ? `(h =6.6 xx 10^(-34)J-s, 1cal = 4.2J)`A. `1.5 xx 10^(13)`B. `2.9 xx 10^(13)`C. `2.3 xx 10^(19)`D. `1.75 xx 10^(19)` |
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Answer» Correct Answer - C Energy received from the sun `= 2 cal cm^(-2) (min)^(-1)` `= 8.4 J cm^(-2) (min)^(-1)` Energy of `1` photon recived from sun, `E = (hc)/(lambda) = (6.6 xx 10^(-34) xx 3 xx 10^(8))/(5500 xx 10^(-10))` `= 3.6 xx 10^(-19) J` `:.` Number of photos reaching the earth per `cm^(2)` per minute will be `n = ("energy received from sun")/("energy of one photon")` or `n = (8.4)/(3.6 xx 10^(-19)) = 2.3 xx 10^(19)` |
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