P1.5 WAVES 1

P1.5 WAVES 1

1. WAVES

   • Waves transfer energy
   • Waves may be either transverse or longitudinal.
   • Electromagnetic Waves= transverse, Sound Waves= longitudinal and Mechanical Waves= Transverse or Longitudinal.
   • All types of electromagnetic waves travel at the same speed through a vacuum
   • TRANSVERSE
     • Electromagnetic waves
     • Waves on strings
     • Ripples in water
     • Spring (up&down)
     • The vibrations are perpendicular to the direction of energy transfer of the wave
   • LONGITUDINAL
     • Sound waves
     • Ultrasound
     • Shockwaves (seismic waves)
     • Spring (pushed at 1 end)
     • Vibrations are parallel to the direction of energy transfer of the wave
     • Longitudinal waves show areas of compression and rarefaction.
   • SPEED(m/s)= FREQUENCY(Hz) * WAVELENGTH (m)
     • All waves obey the wave equation

2. REFLECTION

   • NORMAL= Construction line (imaginary line) perpendicular to the reflecting surface at the point of incidence (where light hits the surface)
   • Angle of incidence= Angle of reflection.
   • Image produced in a plane mirror is virtual.
   • Reflection of light is what allows us to see objects
   • when light travelling in the same direction reflects from an uneven surface (paper), light reflects off at different angles
   • when light travels in same direction reflects from an even surface, then all reflected at the same angle= clear refelction

3. IMAGES FORMED IN A PLANE MIRROR ARE:

   • laterally inverted
   • same size as object
   • same distance behind mirror as object is in front
   • Virtual
     • one that is not made from real light rays (cannot be projected onto a screen)
   • upright

4. REFRACTION

   • when a wave changes direction when entering a more/ less dense medium
   • if a wave meets a different medium at an angle, the wave changes direction (bends towards the normal)
     • when escapes medium, it speeds up as less dense, so ray will bend away from the normal
   • if waves travel along the normal, will change speed and not direction
     • only refracted if they meet at a new medium at an angle
   • occurs when a wave passes through objects of different densities

5. DIFFRACTION

   • when a wave gets spread out when passing through a gap or round an obstacle
   • Narrow gap/ longer wavelength= more wave spreads out
   • Maximum diffraction occurs when the size of the gap/ obstacle is relative to the size of the wavelength