Question

A radiation detector exposed to sunlight records the energy falling on a given area each second. If such a detector has a reading of 0.430 cal cm−2 min−1, how many photons of sunlight are striking each cm2 in one minute? Assume the average wavelength of sunlight is 470. nm. (4.184 J = 1 calorie).

Answer 1

First convert the energy value given from calories to joules.

Next find the energy of one photon of that wavelength, using Planck's equation.

\(\sf E_{photon}=\dfrac{hc}{\lambda}\)

Lastly divide the energy value given by the energy value that corresponds to 1 photon (from equation above).

Answer 2

Thank you! This helps a lot. :)