Waves

Waves

1. Types of waves

   • Mechanical waves
     • A wave that transfers energy through a substance, vibrating particles make nearby particles vibrate.
   • Transverse waves
     • Eg. electromagnetic waves
       • Oscillating electric and magnetic fields that pass through space. The vibrating electric field generates a vibrating magnetic field ect.
     • direction of travel of the wave is perpendicular to the direction of vibrations of the particles
   • Longitudinal waves
     • direction of travel of the wave is parallel to the direction of vibrations of the particles
     • Eg. sound waves
     • On a slinky, each forward movement causes a compression in the wave and each backwards movement causes a rarefraction

2. Polarisation

   • Only transverse waves can be polarised.
   • Plane polarised= vibrations stay in one plane only
   • If vibrations change from one plane to another, the wave is unpolarised.
   • eg of polarised wave- radio waves from a transmitter.
     • aerial of receiver needs to be aligned in same plane as radio waves to get best reception
   • If unpolarised light is passed through two polaroid filters, light intesity changes.
   • if filters are crossed then light intensity is at a minimum and no light can get through.
   • Plane polarisation of an electromagnetic wave is the plane in which the electric field oscillate
   • Polarised sunglasses