课程名称︰普通物理学甲下
课程性质︰数学系大一必带
课程教师︰黄晖理
开课学院：理学院
开课系所︰数学系
考试日期（年月日）︰2014/05/27
考试时限（分钟）：60
试题 :
1. Figure shows an optical fiber in which a central plastic core of index of re-
fraction $n_1$ is surrounded by a plastic sheath of index of refraction $n_2$
(Note: $n_1 > n_2$). Light can travel along different paths within the cen-
tral core, leading to different travel times through the fiber. This causes
an initially short pulse of light to spread as it travels along the fiber,
resulting in information loss. Consider light that travels directly along the
central axis of the fiber and light that is repeatedly reflected at the cri-
tical angle along the core-sheath interface, reflecting from side to side as
it travels down the central core. If the fiber length is L, what is the dif-
ference in the travel times along these two routes? (25 pt.)
https://i.imgur.com/oZNe4Uy.png
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