Question

' $n$ ' polarizing sheets are arranged such that each makes an angle $45^{\circ }$ with the preceeding sheet. An unpolarized light of intensity I is incident into this arrangement. The output intensity is found to be $I/64$. The value of $n$ will be:

• A. 6
• B. 5
• C. 3
• D. 4

Answer 1

Answer: (A)

After passing through first sheet
$I_1=\frac{I}{2}$
After passing through second sheet
$I_2=I_1{\cos }^2\left(45^{\circ }\right)=\frac{I}{4}$
After passing through $n^{\text{th }}$ sheet
$I_n=\frac{I}{2^n}=\frac{I}{64}$
$n=6$