posted by Brian .
We want to rotate the direction of polarization of a beam of polarized light through 90 degrees by sending the beam through one or more polarizing sheets.(a) What is the mini-mum number of sheets required? (b) What is the minimum number of sheets required if the transmitted intensity is to be more than 60% of the original intensity?
Since when can polarizing sheets rotate a linearly polarized light beam?
I don't really know. I did ln(1/100)=-4.605 and ln(cos(90)^2)=-1.605 and 4.605/1.605=2.869. The answer for part (a) should be 2 but 2.869 is closer to 3 so am I doing anything wrong?
(a)If we place one sheet with its polarization direction 90⁰ to the polarized light then the transmitted intensity will be zero (since I=I₀•cos²α = I₀•cos²90⁰=0).
If we use 2 sheets, the 1st sheet rotates by angle α (0< α<90⁰) and the 2nd sheet rotate by the angle (90⁰-α)
Thus, we need two sheets.
I ո ≥0.6•I₀
Thus, the minimum value n=5 sheets.
I still don't understand part (a). I know that cos^2(90)=0 but how did you get to the answer of 2 sheets?
2 because....that's the minimum no. of angles of that can ad up to 90