Diffraction, Reflection and Refraction

Diffraction, Reflection and Refraction

1. Diffraction

   • Waves pass through a gap and spread out
     • Most pronounced when wave length is similar to the gap size

2. Reflection

   • Angle of incidence = angle of reflection
   • All angles measured from the normal
   • Average uncertainty
     • If you have two different degrees for the same angle
       • 80 and 82 the average is 81
         • Can only be out by 1
           • so 1/81 is the average uncertainty

3. Refraction

   • When light passes from one substance to another it changes speed
     • This can cause the light beam to change direction
   • Refractive indicies
     • n = sin(bigger angle)/ sin(smaller angle)
   • When light travels from higher to lower refractive index it bends away from the normal

4. Total internal reflection and the critical angle

   • Below the critical angle
     • Reflected ray gets brighter as i increases
   • At the critical angle
     • The refracted ray disperses into a spectrum with blue closest to the face
       • Blue Bends Best
   • Above the critical angle
     • All light reflected from boundary- TIR
   • Uses of TIR
     • Optical Fibres
     • Endoscope
     • Cat's eyes
     • Reflective clothing

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