[填空题]
Unpolarized light falls o3su.d n vtesw ffg+/y*,ian3 9n two polarira*pfo ri0ln0 61nq)x jm3y :dzer sheets whose transmission axes are at right angles. A third polarizer is placed between the fir)r6 r3 0 xfl1qyj*mnan0 o:pdist two so that its axis makes a 62$^{\circ}\,$ angle with the axis of the first polarizer.
(a) What fraction of the incident light intensity is transmitted? $I_0$
(b) What if the third polarizer is in front of the other two?
