The glass of optical fibre has a refractive index 1.55 and cladding with another glass of refractive index 1.51 . When the surrounding medium is air, the numerical aperture will be

Question

The glass of optical fibre has a refractive index 1.55 and cladding with another glass of refractive index 1.51 . When the surrounding medium is air, the numerical aperture will be (A) 0.625 (B) 0.350 (C) 0.528 (D) 0.704

Tardigrade Admin · Accepted Answer

For air, μ 0=1 . Here, μ 1=1.55, μ 2=1.51 NA=(√μ 12 - μ 22/μ 0) =(√(1.55)2 - (1.51)2/1)=0.350

Q. The glass of optical fibre has a refractive index $1.55$ and cladding with another glass of refractive index $1.51$ . When the surrounding medium is air, the numerical aperture will be

$0.625$

$0.350$

$0.528$

$0.704$

For air, $μ_{0} = 1$ . Here, $μ_{1} = 1.55, μ_{2} = 1.51$
$N A = \frac{μ _{1}^{2} - μ _{2}^{2}}{μ _{0}}$
$= \frac{( 1.55 ) ^{2} - ( 1.51 ) ^{2}}{1} = 0.350$

Q. The glass of optical fibre has a refractive index 1.55 and cladding with another glass of refractive index 1.51 . When the surrounding medium is air, the numerical aperture will be

0.625

0.350

0.528

0.704