Optical Path Length (OPL) refers to the product of the physical distance light travels through a medium and the refractive index of that medium. It helps in understanding how light behaves as it moves through different materials, such as air, water, or glass. OPL is crucial in fields like optics and photography, where precise control of light is necessary. In practical terms, OPL can affect the focus and clarity of images in devices like cameras and microscopes. By calculating OPL, scientists and engineers can design better optical systems, ensuring that light reaches its destination effectively and efficiently.