Now,
(sin
/sin
) max
max
i
r
= 1 68 , which gives imax  ~  60° Thus, all
incident rays of angles in the range 0 < i < 60° will suffer total
internal reflections in the pipe (If the length of the pipe is
finite, which it is in practice, there will be a lower limit on i
determined by the ratio of the diameter to the length of the
pipe