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Homework Statement
Light is shining perpendicularly on the surface of the Earth with an intensity of 910 W/m2. Assuming all the photons in the light have the same wavelength (in vacuum) of 668 nm, determine the number of photons per second per square meter that reach the earth.
Homework Equations
The power per area is:
P/A = (# of photons /t /A)*(energy / photon)
E/photon = h nu = hc / lambda
photons /t /A = (P/A) * lambda / hc
The Attempt at a Solution
photons /t /A = (P/A) * lambda / hc
photoms /t /A = (910)*(668x10^-9)/(6.63x10^-34)(3x10^-8) = 3.066x10^21