the figure below depicts a light-ray entering in optical fiber from air being tr
ID: 1417354 • Letter: T
Question
the figure below depicts a light-ray entering in optical fiber from air being transmitted through the fiber by total internal reflection.
(a) If the index of refraction of the fiber is 'n', what is the maximum value of theta, the angle the entering ray makes with the normal to the flat end of the fiber, for which total internal reflection occurs?
(b) when 'n' is greater than a certain value n_0, the light-ray can enter the fiber at any angle theta between 0 and 90 degrees and total internal reflection still occurs inside the fiber what is n_0?
Explanation / Answer
Frm Snell's law
na sin theta a = nb sin theta b
sin theta a = nb/na sin 90
theta a = arc sin (nb/na sin 90)
thet a = arc sin (n/na)
we can call theta a is critical angle above which only the internal refrlection takes place
if n is greater than a cetain value n_0, and the angle of incidence or critical vlue is 0-90 then
if the anlge of incidence is 0 then
sin theta 0 = n/n_0 sin 90 ==> 0 = (n/ n_0) sin 90 ==> n_0 is infinity
if the angle of incidence is 90 then
sin theta 90 = n/n_0 sin 90 ==> 1 = (n/ n_0) sin 90 ==> n_0 = n
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.