Polarization

📋 Teacher notes

• •Light is a TRANSVERSE wave — it vibrates perpendicular to its direction of travel. "Unpolarized" light vibrates in every possible perpendicular direction at once.
• •A polarizer has a transmission axis — it only lets through the component of vibration ALONG that axis, blocking the rest.
• •Only transverse waves can be polarized. Sound is a LONGITUDINAL wave (vibrates along its direction of travel) and cannot be polarized — a useful way to distinguish the two in an exam.
• •Polarizing sunglasses reduce glare because reflected light off water or glass becomes partially polarized (mostly horizontal) — a vertically-oriented lens blocks much of that reflected glare.
• •LCD screens work by controlling the polarization of light passing through liquid crystals sandwiched between two polarizing filters.