1.6 - Total Internal Reflection of Waves

• Conditions for Total Internal Reflection

  • Must be travelling from more dense medium to a less dense medium
  • Angle of incidence must be greater than the critical angle
• Optical fibres use total internal reflection
• optical fibres 


  • An optical fibre is a thin rod of high quality glass

  • Light undergoes repeated total internal reflection and emerges at the other end
• The refractive index is a material property that describes how a material affects the speed of light travelling through it
• The refractive index affects the critical angle of a material
• 2 uses for optical fibres:

  • high speed internet connections
  • endoscopes
• • Optical fibres use total internal reflection to carry information down a glass rod
• Endoscopy uses optical fibres to show images inside the body
• CT scans use a range of X-Ray images to form a 3D image of structures in the body
• Endoscopy is less harmful than CT scans. It uses light rather than X-rays. The ionising properties of X-rays mean that they can damage the DNA in cells.
• CT scans are used to generate more overall images of the body and give 3D images of areas of the body.
• Optical fibres are point to point communication.
• The distance travelled via optical fibres is shorter than that travelled by a microwave signal via satellite
• the speed of the infrared signal through the optical fibre is lower than the speed of the microwave through the air by satellite