In optics, which term refers to the measure of how much a lens converges or diverges light?

The measure of how much a lens converges or diverges light is known as "front surface power." This term specifically refers to the power of a lens, calculated as the inverse of its focal length, and it directly indicates how strongly the lens can bend light rays. A lens with a high power converges light more sharply, resulting in a shorter focal length, while a low power means a less pronounced convergence or divergence of light.

In contrast, optical density pertains to the attenuation of light as it passes through a material, indicating how much light is absorbed or transmitted but not the bending of light itself. The refractive index describes the ratio of the speed of light in a vacuum to the speed of light in the material, influencing how light bends as it enters the lens, but it does not quantify the actual convergence or divergence of light by itself. Curvature radius relates to the geometry of the lens, affecting the lens's shape and thus influencing its optical properties, but it is not a direct measure of how much light the lens converges or diverges.