The problem statement, all variables and given/known data A microscope equipped with an oil filled objective lens with a numerical aperture of 1.2 is used to image the patterned features on a semiconductor substrate. Define what is meant by the numerical aperture and explain why the lens is oil filled. Using the Rayleigh Criteria, define the smallest resolvable features when light of wavelength 633 nm is used to illuminate the substrate and the oil filled objective is use The attempt at a solution Numerical Aperture is a numerical value which indicates the range of angles at which a system can accept/emit light I know d = (0.61[Lambda]) / 2nsinu and NA is nsinu. Therefore d = (0.61*633*10^-9)/2.4 Is this correct? and why is the lens oil filled?