BRAINCAKEConcave Lenses
A concave lens is thinner at its centre than at its edges. It is a diverging lens: it spreads light rays out.
When rays parallel to the principal axis pass through a concave lens, they diverge as if they had come from a point on the same side of the lens as the light source. This point is the principal focus F. Because the rays only appear to come from it, it is a virtual focus. The distance from the centre of the lens to F is the focal length f.
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More in Optics
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- Applications of Total Internal Reflection
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All 21 lessons in Optics · All Edexcel AS-level Physics topics