f3 - optical fibres
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IB Communication topic - F3 Optical fibresTRANSCRIPT
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Refraction
Snell’s Law
.........but as the angle of incidence increases, eventually:
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...you reach the critical angle:
This is the same as saying the angle of refraction is 90°
....but
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𝑅𝑒𝑓𝑟𝑎𝑐𝑡𝑖𝑣𝑒 𝐼𝑛𝑑𝑒𝑥 ( 𝐴𝑖𝑟 𝑡𝑜𝐺𝑙𝑎𝑠𝑠 )=𝑣𝑎
𝑣𝑔
Refractive Index is the ratio of wave speeds in two mediums:
𝑅𝑒𝑓𝑟𝑎𝑐𝑡𝑖𝑣𝑒 𝐼𝑛𝑑𝑒𝑥 (𝐺𝑙𝑎𝑠𝑠𝑡𝑜 𝐴𝑖𝑟 )=𝑣𝑔
𝑣𝑎
So: 1
𝑅𝑒𝑓𝑟𝑎𝑐𝑡𝑖𝑣𝑒 𝐼𝑛𝑑𝑒𝑥 (𝐴𝑖𝑟 𝑡𝑜𝐺𝑙𝑎𝑠𝑠)𝑅𝑒𝑓𝑟𝑎𝑐𝑡𝑖𝑣𝑒 𝐼𝑛𝑑𝑒𝑥 (𝐺𝑙𝑎𝑠𝑠𝑡𝑜 𝐴𝑖𝑟 )=¿
From before:
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When light hits a surface at an angle of incidence bigger than the critical angle then:
TOTAL INTERNAL REFLECTION
None of the light is transmitted ALL the light is reflected
This is the basis of Optical Fibres
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DispersionThis is when signals spread out as they travel along the fibre.
This can cause problems with data
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