Three polarizers are stacked $,$ normal to a central axis, along which is incident a beam of unpolarized light of intensity Io $.$ The first and the third polarizers are perpendicular to each other and the middle polarizer is rotated at an angular frequency $\backslash$omega about the central axis $($light beam$).$ The time dependent intensity of light emerging after the third polarizer will be a$.$ I$($t$)=$ Io $16(1$ cos$4\backslash$omega t$)$ b$.$ I$($t$)=$ Io $8(1$ cos$2\backslash$omega t$)$