3 ms·
In optics, the numerical aperture (NA) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or
by tester756 3y ago
In optics, the numerical aperture (NA) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light.
https://en.wikipedia.org/wiki/Numerical_aperture https://en.wikipedia.org/wiki/Numerical_aperture