Waves

Waves

1. What are waves?

   • Vibrations that transfer energy from place to place without matter being transferred
   • Some must travel through a substance
     • Sound waves & Seismic waves (shock waves travelling through the Earth) are like this.
       • They must travel through medium and medium vibrates as wave travels through
   • The substance is the 'medium' - can be solid, liquid or gas
   • Some don't travel through medium - can but don't have to
     • Visible light, infrared rays, microwaves & other electromagnetic radiation are like this
       • Can travel through empty space
       • Electric and magnetic fields vibrate as the waves travel

2. Types of wave & their properties

   • Transverse
     • They vibrate perpendicular to the direction of energy transfer of the waves
     • e.g. Light Waves
     • e.g. Water waves & S Waves (type of seismic wave)
     • Troughs are the bottom
     • Peaks/Crests at the top
   • Longitudinal
     • e.g. Sound Waves
     • e.g. ultrasound
     • e.g. shock waves
     • Vibrations are parallel to direction of energy transfer of wave
     • Compressions = bunch together
     • Rarefactions = Spread apart
   • Mechanical
     • Not capable of transmitting its energy through a vacuum (space that's empty of matter)
     • They require a medium to transport energy from one location to another
     • e.g. slinky, water, stadium & jump rope waves

3. Frequency, amplitude & wavelength

   • Amplitude = distance between the middle and top/bottom of the wave
   • Frequency = of a wave is number produced in one second OR number of waves produced by a source each second
     • Measured in Hertz (Hz)
   • Wavelength = Length of a full cycle of the wave e.g. from crest to crest

4. Reflection

   • Normal = imaginary line that's perpendicular to surface at point of incidence (where the light hits the surface)
   • ANGLE OF INCIDENCE = ANGLE OF REFLECTION
   • If light travelling in same direction reflects from even surface, it reflects at the same angle = clear reflection
   • If light travelling in same direction reflects from uneven surface, the light reflects in different angles

5. Ray Diagrams for images in a plane mirror

   • The image is virtual (appears behind the mirror), upright and laterally inverted (left and right sides are swapped)