AQA GCSE Power of Lenses (Physics)
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Power of Lenses
A lens forms an image by refracting (bending) light rays.
The more curved the surface of the lens, the more powerful the lens and the more it will refract the light rays.
Convex (converging lens)
Below is an image which shows a low power and high power converging lens.
Look at the difference in the focal length.
The low power lens has a longer focal length, so the principal focus is further from the centre of the lens.
The high power lens, which is more curved has a shorter focal length, so the principal focus is nearer the centre of the lens.
Concave (Diverging lens)
Below is an image which shows a low power and high power concave lens.
Look at the difference in the focal length.
The low power lens has a longer focal length, so the principal focus is further from the centre of the lens.
The high power lens, which is more curved has a shorter focal length, so the principal focus is nearer the centre of the lens.
Practice Question
1. Explain how changing the shape of a lens will affect the power of the lens
2. Describe what is meant by the term power of the lens.
3. Describe the relation ship between power of the lens and focal length.
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