Final answer:
Light is plane polarized when it consists of electric field oscillations in a single plane. This occurs when passing through a polarizer or upon reflection from surfaces like water or glass. Polarized sunglasses are designed to reduce glare by blocking such plane polarized light.
Step-by-step explanation:
You say that light is plane polarized when the light waves consist of electric fields oscillating in a single plane perpendicular to the direction of propagation. This can occur when ordinary light passes through a polarizer, which only allows waves vibrating in one specific plane to pass through. This kind of light is a combination of left-handed and right-handed circularly polarized light that are chiral, meaning they are non-superimposable mirror images of each other.
When checking if sunglasses are polarized, you can verify this by looking through one pair of sunglasses while holding another in front of it and rotating it. If they are polarized sunglasses, you will notice the light will be blocked in two positions due to the polarization of light. This is because when the polarization axes of both pairs are perpendicular to each other, no light passes through the combination of both.
Moreover, light can also become polarized upon reflection, such as off water or glass surfaces, which is often horizontally polarized. Polarized sunglasses, especially those with vertical axes, can reduce glare because they block this horizontally polarized light that is reflected from surfaces.