Why does blue light offer better resolution than red?

Blue light offers better resolution than red because it has a shorter wavelength, which allows for more precise imaging.

In the realm of physics, the resolution of an optical imaging system - a microscope, telescope, or camera, for instance - can be limited by the diffraction of light. This is often referred to as the diffraction limit. The diffraction limit is directly related to the wavelength of the light being used. The shorter the wavelength, the smaller the diffraction limit, and thus the higher the potential resolution.

Blue light has a shorter wavelength than red light. In the visible spectrum, blue light has a wavelength of approximately 450-495 nanometres, while red light has a wavelength of about 620-750 nanometres. This means that when blue light is used in an optical system, it can potentially resolve finer details than red light.

This principle is utilised in various scientific and technological applications. For instance, in microscopy, blue light can be used to achieve higher resolution imaging. Similarly, in astronomy, telescopes that operate in the blue or ultraviolet part of the spectrum can potentially resolve finer details in the images of stars and galaxies.

However, it's important to note that while blue light can offer better resolution due to its shorter wavelength, it also scatters more easily than red light. This is known as Rayleigh scattering. This can cause images to appear blurry or hazy, particularly in systems where the light has to travel through a significant amount of atmosphere or other scattering medium. Therefore, while blue light has the potential for higher resolution, in practice the optimal wavelength for imaging can depend on a variety of factors, including the specific characteristics of the imaging system and the properties of the medium through which the light is travelling.