An optical microscope objective is initially used in air to study micro-structures…
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
An optical microscope objective is initially used in air to study micro-structures and is later adapted for oil immersion while the geometrical arrangement of the lens remains unchanged.
(i) For the air case, the objective receives light of wavelength 600nm and has a half–angular aperture of 40∘. Calculate the minimum resolvable distance dair.
(ii) In the oil-immersion arrangement the medium has refractive index 1.48 and the illumination wavelength is changed to 450nm, the half–angular aperture remaining 40∘. Determine the new minimum resolvable distance doil.
(iii) Find the percentage improvement in resolution achieved when switching from air to oil immersion under the given conditions.
(iv) Give two physical reasons, based on your calculations, that explain why the resolving power improves in the oil-immersion case.