Intensity of light through two polarizers and Malus's Law

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SUMMARY

The discussion centers on the behavior of unpolarized light passing through two polarizers oriented at 90 degrees to each other, as described by Malus's Law. When unpolarized light with initial intensity I_0 encounters the first polarizer, the intensity is reduced to I_0/2. Upon passing through the second polarizer, which is perpendicular to the first, the intensity becomes I_2 = 0, confirming that no light can pass through crossed polarizers. This conclusion is a direct application of Malus's Law, which states that the transmitted intensity is proportional to the cosine squared of the angle between the light's polarization direction and the polarizer's axis.

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Linus Pauling
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1. A beam of unpolarized light with intensity I_0 falls first upon a polarizer with transmission axis theta1 then upon a second polarizer with transmission axis theta2, where theta2 - theta 1 = 90 degrees (in other words the two axes are perpendicular to one another). What is the intensity I_2 of the light beam emerging from the second polarizer?



2. Malus's Law



3. Would the answer be 0.25I0, i.e. the intensity is cut in half each time, so the final intensity is 1/4 the initial intensity?
 
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Actually, is it just 0?
 
Can light go through the crossed polarizers?

Half the intensity is transmitted if the incident beam is unpolarized, but after the first polarizer, it is polarized.


ehild
 

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