BRAINCAKEThe Power of Twin Lenses
When two thin lenses are placed in contact, they act like a single lens. The power of the combination is the sum of the individual powers:
P = P1 + P2
This is one reason power is useful: powers simply add, whereas focal lengths do not. To find the combined focal length, add the powers first and then use f = 1/P.
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Key terms in this lesson
- chromatic aberration
- A defect of a lens in which light of different colours is refracted by different amounts, so it is brought to different focal points.
- 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
- Applications of Total Internal Reflection
- Concave Lenses
- Convex Lenses
- The Power of a Lens
- Forming an Image
- Image Calculations
- Magnification
- Plane Polarisation
All 21 lessons in Optics · All Edexcel AS-level Physics topics