How is the power of a lens calculated?

How is the power of a lens calculated?

• A. P = f/1, where f is the focal length in meters
• B. P = 1/f, where f is the focal length in meters
• C. P = f², where f is the focal length in meters
• D. P = f + d, where d is the distance to the object

Answer: (B)

The power of a lens is defined as the reciprocal of its focal length measured in meters. This relationship is expressed mathematically as P = 1/f, where P is the power in diopters and f is the focal length in meters. This means that a shorter focal length results in a higher power, indicating a stronger lens. The reason this formula is significant stems from how lenses manipulate light. A lens with a short focal length bends light rays more sharply and, therefore, has a greater ability to converge or diverge the light. This property is crucial in applications ranging from eyeglasses to cameras and optical devices. Understanding this relationship helps comprehend how different lenses can be categorized based on their focal length and strength. The inverse relationship inherently shows that as focal length decreases, lens power increases, suggesting that lenses designed for specific optical needs can be engineered accordingly. This is foundational in the study of optics and lens design.

The power of a lens is defined as the reciprocal of its focal length measured in meters. This relationship is expressed mathematically as P = 1/f, where P is the power in diopters and f is the focal length in meters. This means that a shorter focal length results in a higher power, indicating a stronger lens.

The reason this formula is significant stems from how lenses manipulate light. A lens with a short focal length bends light rays more sharply and, therefore, has a greater ability to converge or diverge the light. This property is crucial in applications ranging from eyeglasses to cameras and optical devices.

Understanding this relationship helps comprehend how different lenses can be categorized based on their focal length and strength. The inverse relationship inherently shows that as focal length decreases, lens power increases, suggesting that lenses designed for specific optical needs can be engineered accordingly. This is foundational in the study of optics and lens design.