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The energy flux of sunlight reaching the surface of earth is 1.388 × 103 W/m2 . How many photons (nearly) per 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» Energy of each photon E = hc/λ = (6.63 x 10-34 x 3 x 108/550 x 10-9) = 3.62 x 10-19 J Number of photons incident on earth’s surface per second per square metre = (Total energy per square metre per second/ Energy of one photon) = (9.388 x 103/3.62 x 10-19 ) = 3.8 x 1021. |
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