Question

At noon on a clear day, sunlight reaches the earth\'s surface at Madison, Wisconsin, with an average power of approximately 1.00 kJ·s–1·m–2. If the sunlight consists of photons with an average wavelength of 510.0 nm, how many photons strike a 1.30 cm2 area per second?

Answer 1

E = hc/wavelength = 6.626E-34*3E8/510E-9 = about 4E-19 J/photon but you need to do it more accurately.

1000 J/s*m^2 x 1.3 c (1 m/100 cm) x (1 m/100 cm) = ?P = power of sun hitting a 1.3 cm^2 area.
Then 4E-19 J/photon x #photons = ?P
Solve for # photons.