Total Internal Reflection

• TIR = light is trapped in a heavier material
• Bigger angle = bigger refraction
• air into glass = refraction: because light changes speed, changes direction

  
• Glass into air - critical angle: travels along the boundary (only if moving from denser material)

  
• Total internal Reflection = in a more dense material, angle is bigger than critical angle

  
• Uses for TIR = Fibre optic cables; endoscope; CAT scan
• Cladding = stops scratches to the core, light getting lost; less dense than core to allow for TIR

  
• A bent cable = changes angles of reflection, slower internet