A linearly polarized electromagnetic wave has an average intensity of 225 W/m 2

Question

A linearly polarized electromagnetic wave has an average intensity of 225 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 = 25.6° with the incident electric field. Polarizer B has its axis at an angle of ?2 = 77.9° with the incident electric field, as shown in the figure.

a. What is the average intensity of the wave after it passes through polarizer A?

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

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

Explanation / Answer

intensity after passing through polariser = I0cos(theta)^2

where theta = angle b/w E field and polariser

I = 225cos(25.6)^2

=182.992928779 watt/m2

now this wave is now polarised in the axis 25.6 with original axis

now intensity passed = (182.992928779)cos(77.9-25.6)^2

=68.4330093293 watt/m2

if these are interchanged

I =225 cos( 77.9)^2 cos(77.9-25.6)^2

=3.69720325737 Watt/m2

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