Which aspect is crucial when considering the power of a lens?

The focal length of a lens is a fundamental property that directly influences its optical power. In optics, power is defined as the inverse of the focal length, measured in meters. This means that a shorter focal length corresponds to a higher power, allowing the lens to bend light more sharply. A lens with a longer focal length will have a lower power because it bends light less intensely.

By understanding the relationship between focal length and power, one can infer that a strong lens, like those used in magnifying glasses or corrective eyewear, needs to have a short focal distance to effectively converge or diverge light rays. This characteristic plays a pivotal role in applications ranging from everyday optical devices to advanced imaging systems, making it an essential consideration when evaluating lens performance.