Total Internal Reflection

Total Internal Reflection

1. Optical Fibres

   • carry visible light over long distances
   • work (because of total internal reflection) by bouncing waves off the sides of a thin inner core of glass or plastic
     • wave enters one end of the fibre and is reflected repeatedly until it emerges at the other end

2. Critical Angle

   • dense material with a high refractive index
     • low critical angle
       • Critical angle of glass: 42* Critical angle of diamond: 24*
         • why diamonds sparkle
   • material with high refractive index
     • will totally internally reflect more light
       • more light will be incident at an angle bigger than the critical angle

3. Endoscopes

   • a thin tube containing optical fibres
     • lets surgeons examine inside the body
   • consists of two bundles of optical fibres
     • one: carry light to the area of interest
     • other: carry an image back so that it can be viewed
       • image seen through an eye-piece or displayed as a full-colour on a TV screen
   • Big Advantage
     • Surgeons can perform many operations by only cutting teeny holes in people (called keyhole surgery)

4. happen when

   • a wave travels through a dense substance like glass or water towards a less dense substance like air

5. if the angle of incidence is

   • Less than Critical angle
     • most of the light passes out
     • little bit is internally reflected
   • equal to Critical angle
     • emerging ray comes out along the surface
     • quite a bit of internal reflection
   • greater than Critical Angle
     • No light comes out
     • All internally reflected i.e. total internal reflection

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