Question

At noon on a clear day, sunlight reaches the earth\'s surface at Madison, Wisconsin, with an average power of approximately 4.00 kJ·s–1·m–2. If the sunlight consists of photons with an average wavelength of 510.0 nm, how many photons strike a 5.10 cm2 area per second?

Answer 1

E= hc/wavelength
E = 6.626E-34J*3E8 m/s/510E-9m
?J/photon.

?J/photon x #photons = 4000J/m^2 x 5.10 cm^2 x (100 m/cm) x (100 m/cm)

Substitute for ?J/photon and solve for # photons.
The number on the right changes kJ to J and cm^2 to m^2.
Post your work if you get stuck or have questions.

Answer 2

9.13x10^26