Reflection, diffraction and refraction of waves

Reflection, diffraction and refraction of waves

1. all waves can be reflected, diffracted and refracted

2. Reflection of Light

   • when light travelling in the same direction reflects from an uneven surface such as a pice of paper the light reflects off a different angles.
   • when light travelling in the same direction reflects from an even surface (smooth and shiny like a mirror) then its all reflected at the same angle and you get a clear reflection
     • ray diagrams
       • the image is the same size as the object
       • it is as far behind the mirror as the object is in front
       • the left side and right sides are swapped i.e the objects left side becomes its right side in the image
       • for an image on a plane mirror
   • the angle of incidence is equal to the angle of reflection

3. Diffraction of waves

   • waves spreading out
   • the amount of diffraction depends on the size of the gap relative to the wavelength of the waves
   • the narrower the gap, or the longer the wavelength, the more the wave spreads out
     • the wider the gap the less the waves spread out because it is bigger than the wavelength
   • maximum diffraction occurs when the gap is about the same width as the wave length of the waves

4. Inerference

   • all waves can cause some kind of disturbance in a medium
   • when two identical waves meet at a point they both try to cause their own disturbance
   • Constructive interference
     • waves disturb in the same direction and reinforce each other
   • destructive interference
     • waves disturb in opposite directions and cancel each other out

5. Refraction

   • waves travel at different speeds in substances which have different densities
   • so when a wave crosses a boundary between two substances, from glass to air it changes speed
   • when light enters a more dense medium it slows down and refracts towards the normal line
     • when it enters a lens dense medium it speeds up and refracts away from the normal.
   • angle of refraction is always less than the angle of incidence

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