Numerical Aperture of an Optical fibre
This CalcTown calculator calculates the numerical aperture of an optical fibre, which is a measure of the light-gathering power of the fibre.
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NA is the Numerical Aperture of the optical fibre
θ is the angle the ray makes with the fiber axis, before entering the fiber,
n0 is the refractive index of the surrounding medium
n1 is the refractive index along the central axis of the fiber, and
n2 is the refractive index of the cladding.