I n t r odu ci n g Fi ber Opt i cs
Fiber optic cables car r y the signals that m ake up our em ails, texts and voice
calls acr oss the globe at an astounding speed by taking advantage of the
pr oper ties of light. The specific pr oper ty of light / m atter inter action that
fiber optic cables r ely on is called Total Inter nal Reflection.
M at er i al s
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Red or Gr een Laser or Laser Blox
Lum i Rod Fiber Optic Dem onstr ator
Acr ylic Refr action Block
Pr otr actor
Han ds On
1. Ex pl or e Tot al I n t er n al Ref l ect i on - If you look at the r ight angle, a
tr anspar ent angle can r eflect light better than any m ir r or. To obser ve
the phenom enon, point the laser into the acr ylic block so that it enter s at
an angle. Adjust the angle until you notice that the beam no longer
passes thr ough the block , but r eflects off the inner edge just like in the
im age.
2. Fi n d t h e cr i t i cal an gl e -Using a pr otr actor to m easur e the incident and
r eflected angels, find the angle at w hich no beam is tr ansm itted and
near ly 100% of the beam is r eflected,. This is the Cr itical Angle.
3. Obser ve Li gh t Tr an sm i ssi on - Total inter nal r eflection helps tr ansm it
telecom m unications data along optical fiber s. Any light that is not
aligned par allel to the axis of the fiber hits the w all of the fiber and is
r eflected (totally!) back inw ar d, since the angle of incidence w ith w hich
the light hits the w all is m uch lar ger than the cr itical angle . This
pr events the signal fr om w eakening as it tr avels a long distance.