Homework Solution

TQ 12-2

No. There is a minimum energy required to create an electron-hole pair. If the photon's energy is less than this minimum, the electron-hole pair cannot be created.

Since the energy of a photon is

E_photon = h f

and

c = lf

then

E_photon = h c / l

To create an electron-hole pair, the minimum energy required must be supplied by the photon, or

E_photon,min = E_e-h

E_e-h = h c / l_max

or

l_max = h c / E_e-h

All wavelengths greater than l_max cannot produce an electron-hole pair.

A light filter only reduces the intensity of the light (the number of photons per unit area per unit time) striking the solar call; it cannot change the frequency or wavelength of the light.