Waves P1

Waves P1

1. Progressive Waves

   • Progressive wave= wave that transfers energy from one place to another
   • Transverse Waves= vibration of particles/ field is perpendicular to the direction of travel of the wave
   • Longitudinal Waves= vibrations of particles/ field is parallel to the direction of travel
   • Displacement= distance (and direction ) from equilibrium position
     • Amplitude= Maximum Displacement
       • Frequency= wave cycles passing a point per second
         • Time period- time taken for one oscillation
   • Wavelength- least distance between 2 identical points
     • speed- c= f x wavelength
       • Phase Difference- fraction of a cycle between two oscillations
         • Path Difference= Difference between distance travelled by each wave from a source to that point
         • 1 cycle= 350 degrees= 2pie radians

2. Longitudinal Vs. Transverse

   • Longitudinal= parallel to direction of travel
     • Examples: sound waves, primary seismic waves, slinky (compressions) etc.
   • Transverse= Perpendicular to Direction of travel
     • Examples: Em waves, Secondary seismic waves and waves on a string
     • Polarisation- so that oscillations are made to occur in 1 plane only
       • Arial Alignment- radio waves from a transmitter is polarised, aerial of a radio receiver is aligned in the same plane to obtain the best reception
       • Polaroid Sunglasses- light reflected by water or glass is slightly polarised, so it's intensity can be reduced using polariod sunglasses- reducing glare

3. Refraction at a Plane Surface

   • Refractive index = speed of light in vacuo/ spped of light in substance
   • Refraction is the change of direction a wave undergoes when it enters a medium with a different refractive index
   • Slows down= towards the normal, speeds up= away from the normal
   • Snell's Law: N1 x sinex angle1 = N1 x sine x angle 2
   • Total Internal Reflection: e.g light travels from glass to air it speeds up and refracts away from the normal, if the angle of incidence is increased to the critical angle, it refracts along the boundary, if the angle is increased further he light ray undergoes total internal reflection
     • Sine critical angle= n2/n1