We present the results of a theoretical study for the interpretation o
f the optical and magneto-optical spectra of PrSb. In particular, we a
ddress the question of the assignment of the unexpectedly low optical
and magneto-optical signals to the f2 --> f1d transition. We use two d
ifferent approaches: the crystal-field approach, suitable for the Pr 4
f states assumed to be localized, and the band approach for the conduc
tion electrons polarized by the 4f states. The two pictures are merged
by the technique of a fixed 4f spin moment used to perform the spin-p
olarized calculations for the conduction electrons. We calculate the 4
f spin moment mu4f(s) in the crystal-field ground state of Pr3+ includ
ing the molecular-field correction lambdaM. From the local spin densit
y approximation calculations we evaluate the molecular-field constant
lambda, which agrees with the previous value, the interband conductivi
ty, reflectivity, and the Kerr rotation angle for the conduction elect
rons. On the basis of our model we find that the weak intensity of the
optical and magneto-optical signal is ascribable essentially to elect
ric dipole selection rules among crystal-field states. Finally, we int
erpret the structure at congruent-to 1 eV in the off-diagonal conducti
vity spectrum in terms of the f2 --> f1d transition. This is in agreem
ent with two different reflectivity spectra.