JEE Main · 2023 · 29 Jan 2023 · Shift 2 · Geometrical Optics

The resolving power of a microscope is $\frac{2\mu \sin \theta }{1.22\lambda }$, so it rises when the refractive index $\mu$ of the medium between object and objective is increased, when the wavelength $\lambda$ is decreased, or when the aperture angle $\theta$ is widened. Lengthening the wavelength or narrowing the objective would both lower it, and the eyepiece focal length governs magnification rather than resolution. Filling the gap with a higher-index medium, as in oil immersion, raises the resolving power.