A linearly polarized electromagnetic wave has an average intensity of 181 W/m 2

Question

A linearly polarized electromagnetic wave has an average intensity of 181 W/m2. This wave is directed towards two ideal polarizers (in real polarizers, transmission is also effected by reflection and absorption). Polarizer A is oriented with its transmission axis at an angle of 1 = 35.5° with the incident electric field. Polarizer B has its axis at an angle of 2 = 71.4° with the incident electric field, as shown in the figure.

What is the average intensity of the wave after it passes through polarizer B?

Suppose that the two polarizers A and B are interchanged. What would the average intensity be after passing through both polarizers
?

Explanation / Answer

Malus law

I=Io Cos(t)

Ia = 181 w/m2 * cos(35.5) = 147.354 w/m2 : intensity after A polariser

Ib = 147.354 w/m2 * cos(71.4) = 46.999 W/m2 : Intensity after polariser B

If we inter change

Ia = 181 w/m2 * cos(71.4) = 57.731 w/m2

Ib = 57.731 w/m2 * cos(35.5) = 46.999 w/m2

Average intensity same in both cases

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