An analyser is inclined to a polariser at an angle of ${30}^0$ . The intensity of light emerging from the analyser is $\frac{1}{n}{}^{{}^{th}}$ of that is incident on the polarizer. Then n is equal to

Here ,  $\theta ={30}^0$ ,$I=\frac{I_0}{n}$

Intensity of polarized light $I=\frac{I_0}{2}{\cos }^2\theta$

                                           $\frac{I_0}{n}=\frac{I_0}{2}{\cos }^{2}30$

                                                 $\Rightarrow \frac{I_0}{2}.\frac{3}{4}$

                                         $\frac{I_0}{n}=\frac{3I_0}{8}$

                                       $\therefore n=\frac{8}{3}$