Question

What will happen to the parameters of an optical fiber, when it is submerged into water i) numerical aperture and ii) acceptance angle?

Answer 1

1.

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

NA will decrease.

2.

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

AA will decrease.