Consult Multiple-Concept Example to see a model for solving this kind of problem. You are using a microscope to examine a blood sample. Recall from Section that the sample should be placed just outside the focal point of the objective lens of the microscope.
(a) If the specimen is being illuminated with light of wavelength λ and the diameter of the objective equals its focal length, determine the closest distance between two blood cells that can just be resolved. Express your answer in terms of λ.
(b) Based on your answer to (a), should you use light with a longer wavelength or a shorter wavelength if you wish to resolve two blood cells that are even closer together?