Question

• The numerical aperture of an
optical fibre is 0.43 and the core
refractive index is 1.61. Find the
refractive index of cladding.
Answer
A. 1.85
B.
1.55​

Answer 1

Answer:

1.48

I think that this is the answer

Answer 2

Answer:

The cladding's refractive index, $\mu_{cladding}$, measured is $1.55$.

Therefore, option b) $1.55$ is correct.

Explanation:

Given,

The given numerical aperture of an optical fibre, N.A = $0.43$

The core's given refractive index, $\mu_{core}$ = $1.61$

The cladding's given refractive index, $\mu_{cladding}$ =?

As we know,

• The core's refractive index is always greater than the cladding's refractive index.

Now,

• $(N.A)^{2} = (\mu_{core} )^{2} -(\mu_{cladding})^{2}$

Therefore,

• $\mu_{cladding}$ = $\sqrt{ (\mu_{core})^{2} -(N.A)^{2} }$
• $\mu_{cladding}$ = $\sqrt{(1.61)^{2} - (0.43)^{2} }$
• $\mu_{cladding}$ = $\sqrt{2.59- 0.184}$
• $\mu_{cladding}$ = $\sqrt{2.406}$ = $1.55$

Hence, the cladding's refractive index, $\mu_{cladding}$, calculated is $1.55$.