Two polaroid are kept crossed to each other. Now one of them is rotated through an angle of 450 . The percentage of incident light now transmitted through the system is

Polarizer absorb electric field perpendicular to its axis therefore intensity becomes I0/2  after passing through polaroids and  after that as per Malus' law becomes I=I0/2cos245 ∴ I=I0/4⇒25%