Refraction

• Refraction


  When light waves are bent when they enter a new media (which is a posh word for material)
• Waves Changing Direction at a Boundary

  1. When a wave crosses a boundary between materials at an angle, it changes direction-it's refracted

  2. How much it's refracted by depends on how much the wave speeds up or slows down, which usually depends on the density of the two materials (usually the higher the density of a material, the slower a wave travels through it)

  3. If a wave crosses a boundary and slows down it will bend towards the normal

  4. If it crosses into a material and speeds up it will bend away from the normal
• The wavelength of a wave changes when it is refracted, but the frequency stays the same
• If the wave is travelling along the normal it will change speed, but it's NOT refracted
• If a light wave hits the boundary 'face on', it carries on in the same direction, but if a wave meets a different medium at an angle, the wave changes direction - it's been REFRACTED
• The wave fronts being closer together shows a change in wavelength (and so a change in velocity)
• Optical density


  A measure of how quickly light can travel through a material - the higher the optical density, the slower light waves travel through it
• Constructing a Ray Diagram to show Refraction

  1. Draw the boundary between your two materials and the normal (a line at 90° to the boundary)

  2. Draw an incident ray that meets the normal at the boundary. The angle between the ray and the normal is the angle of incidence

  3. Draw the refracted ray on the other side of the boundary. If the second material is optically denser than the first, the refracted ray bends towards the normal. If the second material is less optically dense, the angle of refraction is larger than the angle of incidence