Answer:
35.7 mW
Explanation:
The intensity of light after passing through a polarizer is given by
[tex]I=I_0 cos^2 \theta[/tex]
where
[tex]I_0[/tex] is the initial intensity of the light
[tex]\theta[/tex] is the angle between the direction of polarization of the initial light and the transmission axis of the polarizing filter
Keeping in mind that the power is directly proportional to the intensity:
[tex]P \propto I[/tex]
we can rewrite the previous equation as
[tex]P=P_0 cos^2 \theta[/tex]
where we have
[tex]P_0 = 200 mW[/tex]
[tex]\theta=90^{\circ}-25^{\circ}=65^{\circ}[/tex] (because the initial light is horizontally polarized, while the axis of the filter is 25 degrees from the vertical
So, the power of the laser beam emerging from the filter is
[tex]P=(200 mW) cos^2 65^{\circ}=35.7 mW[/tex]
