How does the wavelength of light affect microscope resolution?

In microscopy, the resolution—the ability to distinguish two closely spaced points as separate—is fundamentally limited by the diffraction of light. When the dimensions of an object approach the wavelength of the light being used, diffraction effects become significant, complicating image formation.12

The wavelength of light directly influences resolution because each spatial frequency component of an object produces diffraction at an angle dependent upon that wavelength. To resolve finer details, an objective must be able to collect these diffracted waves. Because the aperture of an objective is limited, it can only capture a certain number of these waves; the more waves collected, the finer the detail that can be reconstructed.2

Consequently, resolution can be improved by using light with a shorter wavelength. Furthermore, when light propagates through a denser medium, its effective wavelength is reduced, which allows for the resolution of even finer details. This principle is utilized in immersion objectives, where a medium with a higher refractive index increases the numerical aperture and enhances the microscope's resolving power.12