Converging & Diverging Lenses (Edexcel A Level Physics)

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Converging & Diverging Lenses

  • A lens is a piece of equipment that forms an image by refracting light
  • There are two types of lens:
    • Convex
    • Concave

Convex Lenses

  • In a convex lens, parallel rays of light are brought to a focus by refraction
    • This point is called the principal focus

  • This lens is sometimes referred to as a converging lens
  • The distance from the lens to the principal focus is called the focal length
    • This depends on how curved the lens is
    • The more curved the lens, the shorter the focal length

Lens focus, IGCSE & GCSE Physics revision notes

The focal length is the distance from the lens to the principal focus

Concave Lenses

  • In a concave lens, parallel rays of light are made to diverge (spread out) from a point
    • This lens is sometimes referred to as a diverging lens

  • The principal focus is now the point from which the rays appear to diverge from

Diverging Lens, downloadable IGCSE & GCSE Physics revision notes

Parallel rays from a concave lens appear to come from the principal focus

Exam Tip

To remember which lens is converging or diverging, think of the following: Convex lens = Converging

To remember which lens is which, a concave lens goes in at the middle, like a cave. Okay, not a very exciting cave, but all the same...

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Author: Ashika

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