What is 'chromatic aberration' in optics?

Chromatic aberration is a phenomenon that occurs in optics when a lens is unable to focus all wavelengths of light to the same convergence point. This is due to the fact that different wavelengths of light (colors) have different refractive indices when passing through a lens material, which causes them to bend at different angles. As a result, this leads to a distortion of color in images, where colors may appear fringed or blurred, particularly at the edges of the image.

This explanation underscores why the choice identifying the distortion of color due to different refractive indices is the correct answer. The other options do not accurately capture the essence of chromatic aberration. For instance, the blurring of images caused by the wrong focal length can encompass a variety of issues that extend beyond chromatic aberration. Similarly, the inability of a lens to focus light correctly could refer to other types of optical aberrations, such as spherical aberration. Lastly, while different angles of incidence for various wavelengths can imply some dispersion effects, it doesn't directly define chromatic aberration in terms of color distortion which is the core aspect of the phenomenon.