A heating device uses a converging lens to bring a beam of parallel light to a focus as close to the lens as possible.
A technician tests two converging lenses made from the same glass.
| lens | measured quantity | value |
|---|---|---|
| J | focal length | 0.28 m |
| K | power | +4.0 D |
Calculate the power of lens J.
Explain which lens should be used in the heating device. In your answer, predict how the curvature of the surfaces of this lens compares with the other lens.
93 exam-style questions on Edexcel GCSE Physics 5.1 Reflection, refraction and lenses, covering 5.1.1 Reflection, refraction and total internal reflection, 5.1.2 Specular and diffuse reflection, 5.1.3 Colour of light: absorption and filters, 5.1.4 Lenses: power, focal length and shape, 5.1.5 Ray diagrams for converging and diverging lenses, and 5.1.6 Real and virtual images. Each one has a worked solution and a mark scheme showing where the marks go.