Q. The glass of optical fiber has refractive index 1.55 and is clad with another glass of refractive index 1.51. When the surrounding is air, the numerical aperture will be
A) 0.625
B) 0.350
C) 0.528
D) 0.704
Explanation
(b) For air,${\ \mu}_{0} = 1$. Here, $\mu_{1} = 1.55,\ \mu_{2} = 1.51$
$NA = \frac{\sqrt{\mu_{1}^{2} - \mu_{2}^{2}}}{\mu_{0}}$
$= \frac{\sqrt{(1.55)^{2} - (1.51)^{2}}}{1} = 0.350$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.