Waves - Physics

Waves - Physics

1. Progressive Waves

   • Mechanical
     • Requires a medium to travel through (e.g. Sound, surface water waves, waves on a string, earthquake waves etc.)
   • Electromagnetic
     • Radio waves
     • All EM waves are transverse in nature
     • Visible light
     • Microwaves
   • Transverse
     • Oscillations are perpendicular to the direction of wave propagation
     • Examples include waves on a string, microwaves, earthquake S waves
   • Longitudinal
     • Oscillations are parallel to the direction of wave propagation
     • Examples include sound waves and earthquake P waves

2. Definitions

   • Displacement (x) of a particle is its distance and direction from its equilibrium position
   • Amplitude (A) is the maximum displacement from the equilibrium position
   • Frequency is the number of oscillations passing a point in the wave per second
   • Period (T) is the time for one whole oscillation (one cycle)
   • Phase difference is the fraction of a cycle difference between the vibrations of two particles
   • Wavelength is the least distance between adjacent which are in phase

3. Useful equations

   • Phase difference = (distance between two points on the wave / wavelength) x 360 (for a displacement distance graph)
   • Phase difference = (time between the two points on the wave/time period) x 360 (for a displacement-time graph)
   • Wave speed = frequency x wavelength
   • Refractive index = speed of light in a vacuum / speed of light in the medium

4. Refraction

   • When waves pass from low to high refractive index (n < n'), they slow down and are refracted towards the normal
   • When waves pass from high to low refractive index (n > n'), they speed up and are refracted away from the normal
   • Snell's law: n1 sin