Summary
Polarisation involves restricting the vibrations of transverse waves to one specific direction while keeping them perpendicular to the wave's direction of propagation. Longitudinal waves cannot be polarized because their oscillations are parallel to the direction of wave travel.
- Transverse Waves — oscillations perpendicular to their direction of travel. Example: Light waves are transverse waves.
- Polarization — restricting vibrations to one direction in transverse waves. Example: Light passing through a polarizing filter becomes polarized.
- Unpolarized Waves — vibrations occur in various planes. Example: Sunlight is unpolarized.
- Polarized Waves — vibrations confined to a specific plane. Example: Light through polaroid sunglasses is polarized.
- Malus's Law — describes intensity reduction of light through a polarizer. Example: Intensity is halved when unpolarized light passes through a polarizer.
- Brewster’s Angle — angle of incidence where light is perfectly transmitted. Example: Light reflecting off water at Brewster's angle is polarized.
Exam Tips
Key Definitions to Remember
- Transverse Waves: Oscillations perpendicular to the direction of travel.
- Polarization: Restricting vibrations to one direction in transverse waves.
- Malus's Law: Describes intensity reduction of light through a polarizer.
Common Confusions
- Confusing transverse and longitudinal waves in terms of polarization.
- Misunderstanding the role of polarizers and analyzers.
Typical Exam Questions
- What happens to light intensity when it passes through a polarizer? It is reduced by half.
- How does Brewster’s angle affect light? Light is perfectly transmitted and polarized at this angle.
- Why can't longitudinal waves be polarized? Their oscillations are parallel to the direction of wave travel.
What Examiners Usually Test
- Understanding of how polarization affects light intensity.
- Ability to explain why longitudinal waves cannot be polarized.
- Application of Malus's Law in calculating light intensity.