[填空题]
Unpolarized light passes througq0k8 xs1m(kchc2 dno2h fekn+d i1y5s c:e(v8 u bh6y yi3ds0pp5ive successive Polaroid sheets, each of whose axupcv5k 1yddp8e(e0s:y 6b3 hysi5+ni is makes a 45$^{\circ}\,$ angle with the previous one. What is the intensity of the transmitted beam? $I_0$
