Working Waves

Working Waves

1. Total Internal Reflection

   • Angle of incidence is greater than the critical angle
   • n = sin i ÷ sin r

2. Thermal Imaging

   • What is a perfect black body?
     • It is an object that omits/absorbs all electromagnetic radiation
   • How are thermal images used?
     • Focuses on the infrared radiation given off by an object using a lens
   • How is it detected?
     • Several thousand detector elements in a focal planes array (flat
   • Applications
     • Fire fighting, weather forecast, find survivors
   • Spatial resolution
     • How we distinguish an object between two different places
   • Thermal resolution
     • How we distinguish an object between two different temperatures

3. Optical Fibres

   • Coherent
     • Fibres are arranged
     • Communication images e.g. endoscope
   • Incoherent
     • Fibres are randomly arranged
     • Light
   • Advantages
     • Large info capacity
     • Low material cost
     • Smaller cable sizes
   • Structure
     • 1. Core
     • 2. Cladding
     • 3. Buffer
     • 4. Jacket
   • Three types
     • Monomode
     • Step index
     • Graded index

4. Wave features

   • Wavelength = Velocity X Time OR Velocity = Frequency X Wavelngth
   • Displacement = the distance a wave moves in a particle from its rest position
   • Transverse Waves
     • Particles at 90 degree wave direction
   • Longitudinal
     • Displacement is parallel to wave direction and therefore not at angles
     • Sound waves