Light from a distant transmitter enters an optical receiver as rays parallel to the principal axis of a converging lens. The lens has a power of +4.0 D+4.0\ \text{D}+4.0 D. A light sensor is 0.30 m from the optical centre of the lens on the opposite side from the transmitter. The sensor needs to be positioned where the rays meet.
Calculate the focal length of the lens.
Explain how the position of the sensor should be changed.
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.