14. Total Internal Reflection and Evanescent Waves

14. Total Internal Reflection and Evanescent WavesPhase shifts in reflectionTotal Internal Reflection and applicationsEvanescent wavesReminder: the Fresnel equations||cos( )cos( )cos( )cos( ) ittiittinnrnn ||2cos()cos( )cos( ) iiittintnn 2cos()cos( )cos( ) iiiittntnn cos( )cos( )cos( )cos( ) iittiittnnrnn s-polarized light:p-polarized light:And, for bothpolarizations: sin( )sin( ) iittnn plane of incidenceincident wavetransmitted waveinterfaceplane of incidenceincident wavetransmitted waveinterface || ititnnrrnn 00 Ifair to glass , at itinnr So there will be destructiveinterference between the incident and reflected beams near the surface, where they overlap in normal incidence, i= 0, we find:Phase Shift in ReflectionNote: for p-polarized light, the sign of r||changes for angles above Brewster s , ifni> nt(glass to air), r > 0, and there will be angle, iReflection coefficient, ||r0 30 60 90 Incidence angle, iReflection coefficient, ||r0 30 60 90 from air to glassBrewster s angleThe obvious answer is the front of the object, which sees the higher intensity constructive interference happens at the back surface between the incident light and the reflected you slowly turn up a laser intensity, where does damage happen first, the front or the back?

Charles Kao (1965): first proposed that fiber could be used as a practical communication technology if the attenuation could be reduced below 20 dB/km. He showed that the loss was dominated by chemical ... Fiber optic sensors rays propagating in a large-core fiber The value of the critical angle depends on the ratio n t /n i. evanescent wave 1 ...

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