Question

The maximum solid angle of acceptance of light coupled into a step index fibre having core and cladding refractive indices of 1.48 and 1.45 respectively, is

• A. 0.32 steradians
• B. 0.28 steradians
• C. 0.30 steradians
• D. 0.34 steradians

Answer 1

The correct option is B 0.28 steradians

Solid angle $=\pi (\sin {\theta }_a{)}^2$
$\because \sin {\theta }_A=\sqrt{n_1^2-n_2^2}=\sqrt{{1.48}^2-{1.45}^2}$
$=\sqrt{0.0879}=0.296$
Solid angle $=0.28\text{steradins}$