Polarization: Unpolarized light passes through three polarizing filters. The first one is oriented with a horizontal transmission axis, the second filter has its transmission axis 25.7° from the horizontal, and the third one has a vertical transmission axis. What percent of the light gets through this combination of filters?
A) 7.6%
B) 92.4%
C) 50.0%
D) 0.00%

Question

Quizplus · Accepted Answer

The intensity of light after passing through multiple polarizing filters is given by Malus's law, which states that the intensity of polarized light after passing through a polarizing filter is proportional to the cosine squared of the angle between the light's initial polarization direction and the axis of the filter. For unpolarized light passing through the first filter, the intensity is reduced by half. The intensity after the second filter is $I_2 = I_1 \cos^2(\theta)$, where $\theta = 25.7^\circ$, and $I_1$ is the intensity after the first filter. For the third filter, since it is vertical and the light is already polarized at 25.7° to the horizontal, the angle to consider is $90^\circ - 25.7^\circ = 64.3^\circ$. Thus, the intensity after the third filter is $I_3 = I_2 \cos^2(64.3^\circ)$. Calculating this gives a small percentage of the original light intensity, which is closest to 7.6%.

Polarization: Unpolarized Light Passes Through Three Polarizing Filters