How to convert Numerical Aperture to F-Number?

Given a telecentric lens with image side numerical aperture N\kern-.3emA. Then

ImageSideFNumber = \frac{1}{2 * \tan (\arcsin ( {N\kern-.2emA_{image}}) ) }
NA = \sin \alpha\alpha = \arcsin (NA)\tan(\alpha) = \tan (\arcsin (NA) )
Also
R = \tan(\alpha) * WD = \tan (\arcsin (NA) ) * WD2*R = 2 * \tan (\arcsin (NA) ) * WDObject Side FNumber = \frac{focal length}{2*R}ImageSideFNumber = Object Side FNumber * Magnification= \frac{focal length}{2*R} * Magnification= \frac{focal length}{2 * \tan (\arcsin ( NA) ) * WD} * Magnification= \frac{Magnification}{2 * \tan (\arcsin ( NA) ) }
Given a telezentric lens with a NA of 0.0042 and a magnification of 0.06x
Then
F = \frac{0.06}{2 * \tan (\arcsin ( 0.0042) )} = 7.14...

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