What does 'f' represent in optical lens formulas?

In optical lens formulas, the symbol 'f' specifically represents the focal length of the lens. The focal length is a critical parameter that defines how strongly the lens converges or diverges light. It is the distance from the lens at which parallel rays of light either converge to a point (in the case of converging lenses) or appear to diverge from a point (in the case of diverging lenses).

Understanding the focal length is essential for predicting how the lens will affect light passing through it, and it plays a key role in applications such as photography, vision correction, and various optical instruments. Knowing the focal length allows one to determine the relationship between the object distance, image distance, and the nature of the resulting image, as described by the lens formula. This foundational concept in optics is a fundamental aspect of how lenses operate and how they are utilized in practical applications.