[填空题]
At what angle should the 1zu wu e49x qwlzm3k,;gi*p7naxes bcb ,k:c9/tpvq *r;9cr x;tyjof two Polaroids be placed so as to reduce the intensity of the incident unpolarized light by an additional fa:;vrbxy qc c bkc9p tr9;,jt*/ctor (after the first Polaroid cuts it in half) of
(a) 4, $^{\circ}\,$
(b) 10, $^{\circ}\,$
(c) 100? $^{\circ}\,$