(a) The thermal energy scale is k_bT, where k_b = 1.38 × 10^-23 J/K is the Boltzmann constant and T is the absolute temperature. What energy does room temperature correspond to? What would be the frequency and wavelength of the corresponding photons? Is it reasonable that a hot body starts to glow around 1000^oC?

(b) What is the photon flux (rate of arriving photons per unit area) at 1 m distance from a 60 W light bulb, if you assume that the bulb conversion efficiency (electrical power to light bulb) is 10% and take the photon wavelength as 500 nm?

(c) A photodiode measures light power by converting incident photons into electron-hole pairs, such that the electron current is proportional to the incident light power. The quantum efficiency is defined as the probability that an incident photon generates an electron. If a typical photodiode has a responsivity of 0.5 A/W for infrared light at 850 nm, what is the quantum efficiency of the device? If the quantum efficiency is independent of frequency, what responsivity do you expect for blue light at 400 nm? Student can find a simulation of black body radiation and related topics (Planck’s law, Wien’s law) at http://csep10.phys.utk.edu/guidry/java/planck/  planck.html.