A 2-cm2 wafer of pure silicon is irradiated with light having a wavelength of 775 nm. The intensity of the light beam is 4.0 W/m2 and every photon that strikes the sample is absorbed and creates an electron–hole pair.

(a) How many electron–hole pairs are produced in one second?

(b) If the number of electron–hole pairs in the sample is 6.25 × 1011 in the steady state, at what rate do the electron–hole pairs recombine?

(c) If every recombination event results in the radiation of one photon, at what rate is energy radiated by the sample?