Question

We want to rotate the direction of polarization of a beam of polarized light through 90° by sending the beam through one or more polarizing sheets. (a) What is the minimum number of sheets required? (b) What is the minimum number of sheets required if the transmitted intensity is to be more than 94% of the original intensity? (a) Number Units (b) Number Units

Answer 1

a)

minimum number of sheets required = 2

b)

from malus law

I = Io cos^(2n) (90 / n)

for n = 1

I = Io cos^2 (90) = 0

for n = 2

I = Io cos^4 (90/2) = 0.25 Io

for n = 3

I = Io cos^6 (90/3) = 0.42 Io

for n = 32

I = Io cos^64 (90/32) = 0.93 Io

for n = 40

I = Io cos^74 (90/37) = 0.94 Io

so 37 is the answer

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