Final answer:
The angle between the two polarizing filters that results in an unpolarized light intensity reduction from 72 W/m^2 to 9 W/m^2 is 60 degrees.
Step-by-step explanation:
The question pertains to the intensity reduction of unpolarized light as it passes through two polarizing filters at a certain angle. When light passes through the first polarizer, its intensity becomes half of the original intensity. The intensity of light after passing through a second polarizer is given by Malus's Law, which states that the intensity I after the second polarizer is I = I0cos2(θ), where I0 is the intensity of the light after the first polarizer, and θ is the angle between the axes of the two polarizers.
Given that the initial intensity is 72 W/m2 (after the first polarizer), and the final intensity is 9 W/m2, we use the relation 9 = (72/2)cos2(θ) to find the angle.
After solving the equation, we find cos2(θ) = 0.25 which implies that cos(θ) = 0.5. Thus, the angle θ is 60°, which is option c.