Question

A step index optical fiber, whose refractive indices of the core and cladding are 1.44 and 1.40 respectively, is surrounded by air. Its numerical aperture is

• A. 0.34
• B. 0.12
• C. 0.06
• D. 0.75

Answer 1

The correct option is A 0.34

$NA=\sqrt{n_1^2-n_2^2}$

$=\sqrt{(1.44{)}^2-(1.40{)}^2}=\sqrt{0.1136}$

$=0.337\approx 0.34$