A student uses an optical microscope in air to observe biological slides.
a. (a) The objective lens has a half–angular aperture of 45∘. Calculate its numerical aperture.
b. (b) If the microscope is illuminated with light of wavelength 600nm, determine the smallest distance between two points that can just be resolved with this objective.
c. (c) If the same objective is used with water as the surrounding medium while keeping the half–angular aperture unchanged, state qualitatively how the resolving limit will change and give a brief reason.