A lens with a focal length of 2 meters has what power?

The power of a lens is calculated using the formula:

[ \text{Power (P)} = \frac{1}{\text{Focal Length (f)}} ]

where the focal length must be in meters, and the resulting power will be in diopters (D). Given a lens with a focal length of 2 meters, you can substitute this value into the formula:

[ P = \frac{1}{2 \text{ meters}} = 0.5 \text{ D} ]

This shows that the power of the lens is indeed 0.5 D. The concept behind this calculation reflects how the focal length relates to the lens's capacity to converge or diverge light. A longer focal length results in a lower power, indicating less optical strength, which is why a focal length of 2 meters corresponds to a power of 0.5 diopters. This aligns with the understanding that lens power and focal length are inversely related.