Abbe number indicates how much a transparent material, such as optical glass or lens elements, disperses light of different wavelengths. It measures the degree of chromatic dispersion: the lower the Abbe number, the greater the separation of colors, which can cause chromatic aberration in photography and optics. High-quality camera lenses and optical instruments are designed with materials that have carefully chosen Abbe numbers to minimize color fringing and ensure sharp, accurate images across the visible spectrum. Understanding Abbe numbers is important for photographers, lens designers, and anyone working with optical systems.