The focal length of a lens is 25 cm. Its power will be

The power of the lens (B) with a focal length of 25 cm will be +4D. Power in diopters (D) is determined by the reciprocal of the focal length in meters. Given that the focal length is 25 cm, which equals 0.25 meters, the calculation for power is 1 divided by 0.25, resulting in +4D. This positive diopter value indicates that the lens converges light rays, focusing them at a point 25 cm away from the lens. Positive diopter values denote converging lenses, used in corrective lenses for conditions like hyperopia (farsightedness) to bring distant objects into focus. Negative diopter values would signify diverging lenses, which spread out light rays and are used for conditions like myopia (nearsightedness). Understanding lens power helps in prescribing appropriate corrective lenses and designing optical systems based on their refractive properties.