Unpolarized light of intensity 21.6 W/cm^2 is incident on two polarizing filters. The axis of the first filter is at an angle of 25.8 degrees counterclockwise from the vertical (viewed in the direction the light is traveling) and the axis of the second filter is at 58.6 degrees counterclockwise from the vertical.
What is the intensity of the light after it has passed through the second polarizer?
What is the intensity of the light after it has passed through the second polarizer?
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Assuming the light is of uniform intensity at all directions the first polarizer would give a polarized light of 21.6 W/cm^2 at angle 25.8 degrees counterclockwise from the vertical. For the next polarizer, you need to break up the 25.8 degree polarized light into X (cosine) and Y (sine) vector components with respect to the angle difference between the first and second filter.
Here,
X=21.6*cos(58.6-25.8) and Y=21.6*sin(58.6-25.8).
Our component of interest here is of course X (if you visualize it by drawing), so X is the intensity of light out of the second polarizer. Try drawing it out, its easier to understand.
PS: This is a matter of shifting the frame of reference suitably according to the source light.
Here,
X=21.6*cos(58.6-25.8) and Y=21.6*sin(58.6-25.8).
Our component of interest here is of course X (if you visualize it by drawing), so X is the intensity of light out of the second polarizer. Try drawing it out, its easier to understand.
PS: This is a matter of shifting the frame of reference suitably according to the source light.