Final answer:
About half of the unpolarized light passes through a polarizing filter and becomes polarized, with the remaining light being absorbed by the filter.
Step-by-step explanation:
When unpolarized light passes through a polarizing filter, option 4 is correct: About half the light passes through and is now polarized. This occurs because polarizing filters allow only the electric field component in one direction to pass through.
As a result, unpolarized light, which initially has its electric field oscillating in all directions, has only the component of its electric field parallel to the filter's axis transmitted, effectively polarizing it.
According to the Malus's law, the intensity of polarized light is given by I = Io cos² θ, where Io is the original intensity and θ is the angle between the direction of polarization and the axis of the filter, this implies that at θ = 0°, half of the incident intensity passes through.