A
particular optical fibre consists of a
non-graded glass core (index
of refraction
|
Solution: Click For PDF Version (a)
As shown in
the figure, let a beam of light enter the optical fibre from air at
incident angle
This beam
hits the glass-coating interface at angle of incidence,
beam that
enters the optical fibre from air will travel by undergoing total
internal reflection. Therefore, the maximum possible value of the
angle
And, therefore,
(b)
For
|
)
surrounded by a cladding (index
of refraction
).
Suppose that a beam of light enters the fibre
from air at angle
with the fibre axis as shown in the figure.
(a) We have to show that the greatest possible
value of
in
the glass is related to
.
.
For
greater than the critical angle
,
determined by the condition that
,
and
,
we find