BRAINCAKEThe Power of a Lens
The power of a lens measures how strongly it converges or diverges light. A lens that bends light more has a shorter focal length and a greater power:
P = 1 / f
f must be in metres. The unit of power is the dioptre (D), which is equal to m-1.
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Key terms in this lesson
- focal length
- The distance from the centre of a lens to the principal focus, where parallel rays converge, or appear to diverge from, after refraction.
More in Optics
- Investigating Total Internal Reflection
- Applications of Total Internal Reflection
- Concave Lenses
- Convex Lenses
- The Power of Twin Lenses
- Forming an Image
- Image Calculations
- Magnification
All 21 lessons in Optics · All Edexcel AS-level Physics topics