The resolving power of an optical microscope is determined by the wavelength of light used and the numerical aperture of the objective lens. The resolving power is the ability to distinguish between two closely spaced objects. The shorter the wavelength of light, the better the resolving power.

Blue light has a shorter wavelength than red light, so it can be used to achieve better resolution in an optical microscope. The shorter wavelength of blue light allows for finer details to be seen in the specimen. Additionally, blue light has a higher energy than red light, so it can be used to excite fluorophores in the specimen, which can further enhance the resolution of the image.

The resolving power of an optical microscope is also affected by the numerical aperture of the objective lens. The numerical aperture is a measure of the light-gathering ability of the objective lens. The higher the numerical aperture, the better the resolving power.

By using blue light and a high numerical aperture objective lens, it is possible to achieve better resolution in an optical microscope. This allows for finer details to be seen in the specimen, and can be particularly useful for studying small structures or cells.